harmonic series - generating function











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I am currently learning about generating functions and
I found an interesting one for harmonic series, $dfrac{log(1-x)}{x-1}$.



Is there any hope I could get a formula for $n$th coefficient out of this? The $n$th derivative looks messy...



In absence of formula, can I at least get some asymptotic information, like that harmonic series diverges? (Can be shown more simply, I know.)










share|cite|improve this question




























    up vote
    3
    down vote

    favorite












    I am currently learning about generating functions and
    I found an interesting one for harmonic series, $dfrac{log(1-x)}{x-1}$.



    Is there any hope I could get a formula for $n$th coefficient out of this? The $n$th derivative looks messy...



    In absence of formula, can I at least get some asymptotic information, like that harmonic series diverges? (Can be shown more simply, I know.)










    share|cite|improve this question


























      up vote
      3
      down vote

      favorite









      up vote
      3
      down vote

      favorite











      I am currently learning about generating functions and
      I found an interesting one for harmonic series, $dfrac{log(1-x)}{x-1}$.



      Is there any hope I could get a formula for $n$th coefficient out of this? The $n$th derivative looks messy...



      In absence of formula, can I at least get some asymptotic information, like that harmonic series diverges? (Can be shown more simply, I know.)










      share|cite|improve this question















      I am currently learning about generating functions and
      I found an interesting one for harmonic series, $dfrac{log(1-x)}{x-1}$.



      Is there any hope I could get a formula for $n$th coefficient out of this? The $n$th derivative looks messy...



      In absence of formula, can I at least get some asymptotic information, like that harmonic series diverges? (Can be shown more simply, I know.)







      generating-functions






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Oct 28 '16 at 17:08









      Michael Hardy

      1




      1










      asked Oct 28 '16 at 16:06









      Adam

      1,45411537




      1,45411537






















          2 Answers
          2






          active

          oldest

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          up vote
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          down vote



          accepted










          $newcommand{bbx}[1]{,bbox[8px,border:1px groove navy]{{#1}},}
          newcommand{braces}[1]{leftlbrace,{#1},rightrbrace}
          newcommand{bracks}[1]{leftlbrack,{#1},rightrbrack}
          newcommand{dd}{mathrm{d}}
          newcommand{ds}[1]{displaystyle{#1}}
          newcommand{expo}[1]{,mathrm{e}^{#1},}
          newcommand{ic}{mathrm{i}}
          newcommand{mc}[1]{mathcal{#1}}
          newcommand{mrm}[1]{mathrm{#1}}
          newcommand{pars}[1]{left(,{#1},right)}
          newcommand{partiald}[3]{frac{partial^{#1} #2}{partial #3^{#1}}}
          newcommand{root}[2]{,sqrt[#1]{,{#2},},}
          newcommand{totald}[3]{frac{mathrm{d}^{#1} #2}{mathrm{d} #3^{#1}}}
          newcommand{verts}[1]{leftvert,{#1},rightvert}$

          With the identity
          $ds{pars{1 - x}^{m} = sum_{k = 0}^{infty}
          {m choose k}pars{-x}^{k} =
          sum_{k = 0}^{infty}{k - m - 1 choose k}x^{k}}$
          :




          begin{equation}
          begin{array}{l}
          mbox{Derivative respect of} ds{m}:
          \
          ds{pars{1 - x}^{m}lnpars{1 - x} =
          sum_{k = 0}^{infty}bracks{partiald{}{m}{k - m - 1 choose k}}x^{k}}
          \[5mm]
          mbox{The limit}ds{ m to - 1}:
          \
          ds{-,{lnpars{1 - x} over 1 - x} =
          sum_{k = 0}^{infty}color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}
          _{ m = - 1}} x^{k}}
          end{array}
          label{1}tag{1}
          end{equation}



          begin{align}
          &color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}_{ m = - 1}} =
          left.vphantom{Huge A}-,partiald{}{m}bracks{Gammapars{k - m} over k!,Gammapars{-m}}rightvert_{ m = - 1}
          \[5mm] = &
          -,{1 over k!},
          {-Gamma, 'pars{k + 1}Gammapars{1} + Gamma, 'pars{1}Gammapars{k + 1}over Gamma^{2}pars{1}}
          \[5mm] = &
          -,{1 over k!}bracks{%
          {-Gammapars{k + 1}Psipars{k + 1} +
          Gammapars{1}Psipars{1}Gammapars{k + 1}}}
          \[5mm] = &
          Psipars{k + 1} - Psipars{1} = color{#f00}{H_{k}}
          \[1cm]
          stackrel{mbox{see} eqref{1}}{implies} & ,,,
          bbox[10px,#ffe,border:1px dotted navy]{ds{%
          -,{lnpars{1 - x} over 1 - x} = sum_{k = 1}^{infty}H_{k}, x^{k}}}
          end{align}





          share|cite|improve this answer






























            up vote
            3
            down vote













            It is useful to notice that multiplication of a series $A(x)=sum_{n=0}^infty a_nx^n$ with the geometric series $frac{1}{1-x}$ transforms the sequence $(a_n)_{ngeq 0}$ to a sequence of sums $left(sum_{k=0}^na_kright)_{ngeq 0}$. We obtain



            begin{align*}
            frac{1}{1-x}A(x)&=frac{1}{1-x}sum_{n=0}^infty a_n x^n\
            &=sum_{n=0}^infty left(sum_{k=0}^n a_kright) x^ntag{1}
            end{align*}



            So, it is sufficient to determine the $n$-th coefficient of $A(x)$ in order to also know the $n$-th coefficient of $frac{1}{1-x}A(x)$.




            Since the series expansion of $-log (1-x)$ is known to be
            begin{align*}
            -log(1-x)=sum_{n=1}^infty frac{x^n}{n}qquadqquadqquad |x|<1
            end{align*}
            it follows from (1)
            begin{align*}
            -frac{log(1-x)}{1-x}&=frac{1}{1-x}sum_{n=1}^infty frac{x^n}{n}
            =sum_{n=1}^infty left(sum_{k=1}^nfrac{1}{k}right)x^n\
            &=sum_{n=1}^infty H_nx^n
            end{align*}







            share|cite|improve this answer























            • I probably wrote the question wrong. I actually started off wanting to sum 1+1/2+1/3+... - so I tried generating functions. By formula for nth coeffiecient I meant something like n*(n+1)/2 for 1+2+3+4+...n
              – Adam
              Oct 30 '16 at 5:59











            Your Answer





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            2 Answers
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            2 Answers
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            active

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            up vote
            2
            down vote



            accepted










            $newcommand{bbx}[1]{,bbox[8px,border:1px groove navy]{{#1}},}
            newcommand{braces}[1]{leftlbrace,{#1},rightrbrace}
            newcommand{bracks}[1]{leftlbrack,{#1},rightrbrack}
            newcommand{dd}{mathrm{d}}
            newcommand{ds}[1]{displaystyle{#1}}
            newcommand{expo}[1]{,mathrm{e}^{#1},}
            newcommand{ic}{mathrm{i}}
            newcommand{mc}[1]{mathcal{#1}}
            newcommand{mrm}[1]{mathrm{#1}}
            newcommand{pars}[1]{left(,{#1},right)}
            newcommand{partiald}[3]{frac{partial^{#1} #2}{partial #3^{#1}}}
            newcommand{root}[2]{,sqrt[#1]{,{#2},},}
            newcommand{totald}[3]{frac{mathrm{d}^{#1} #2}{mathrm{d} #3^{#1}}}
            newcommand{verts}[1]{leftvert,{#1},rightvert}$

            With the identity
            $ds{pars{1 - x}^{m} = sum_{k = 0}^{infty}
            {m choose k}pars{-x}^{k} =
            sum_{k = 0}^{infty}{k - m - 1 choose k}x^{k}}$
            :




            begin{equation}
            begin{array}{l}
            mbox{Derivative respect of} ds{m}:
            \
            ds{pars{1 - x}^{m}lnpars{1 - x} =
            sum_{k = 0}^{infty}bracks{partiald{}{m}{k - m - 1 choose k}}x^{k}}
            \[5mm]
            mbox{The limit}ds{ m to - 1}:
            \
            ds{-,{lnpars{1 - x} over 1 - x} =
            sum_{k = 0}^{infty}color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}
            _{ m = - 1}} x^{k}}
            end{array}
            label{1}tag{1}
            end{equation}



            begin{align}
            &color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}_{ m = - 1}} =
            left.vphantom{Huge A}-,partiald{}{m}bracks{Gammapars{k - m} over k!,Gammapars{-m}}rightvert_{ m = - 1}
            \[5mm] = &
            -,{1 over k!},
            {-Gamma, 'pars{k + 1}Gammapars{1} + Gamma, 'pars{1}Gammapars{k + 1}over Gamma^{2}pars{1}}
            \[5mm] = &
            -,{1 over k!}bracks{%
            {-Gammapars{k + 1}Psipars{k + 1} +
            Gammapars{1}Psipars{1}Gammapars{k + 1}}}
            \[5mm] = &
            Psipars{k + 1} - Psipars{1} = color{#f00}{H_{k}}
            \[1cm]
            stackrel{mbox{see} eqref{1}}{implies} & ,,,
            bbox[10px,#ffe,border:1px dotted navy]{ds{%
            -,{lnpars{1 - x} over 1 - x} = sum_{k = 1}^{infty}H_{k}, x^{k}}}
            end{align}





            share|cite|improve this answer



























              up vote
              2
              down vote



              accepted










              $newcommand{bbx}[1]{,bbox[8px,border:1px groove navy]{{#1}},}
              newcommand{braces}[1]{leftlbrace,{#1},rightrbrace}
              newcommand{bracks}[1]{leftlbrack,{#1},rightrbrack}
              newcommand{dd}{mathrm{d}}
              newcommand{ds}[1]{displaystyle{#1}}
              newcommand{expo}[1]{,mathrm{e}^{#1},}
              newcommand{ic}{mathrm{i}}
              newcommand{mc}[1]{mathcal{#1}}
              newcommand{mrm}[1]{mathrm{#1}}
              newcommand{pars}[1]{left(,{#1},right)}
              newcommand{partiald}[3]{frac{partial^{#1} #2}{partial #3^{#1}}}
              newcommand{root}[2]{,sqrt[#1]{,{#2},},}
              newcommand{totald}[3]{frac{mathrm{d}^{#1} #2}{mathrm{d} #3^{#1}}}
              newcommand{verts}[1]{leftvert,{#1},rightvert}$

              With the identity
              $ds{pars{1 - x}^{m} = sum_{k = 0}^{infty}
              {m choose k}pars{-x}^{k} =
              sum_{k = 0}^{infty}{k - m - 1 choose k}x^{k}}$
              :




              begin{equation}
              begin{array}{l}
              mbox{Derivative respect of} ds{m}:
              \
              ds{pars{1 - x}^{m}lnpars{1 - x} =
              sum_{k = 0}^{infty}bracks{partiald{}{m}{k - m - 1 choose k}}x^{k}}
              \[5mm]
              mbox{The limit}ds{ m to - 1}:
              \
              ds{-,{lnpars{1 - x} over 1 - x} =
              sum_{k = 0}^{infty}color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}
              _{ m = - 1}} x^{k}}
              end{array}
              label{1}tag{1}
              end{equation}



              begin{align}
              &color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}_{ m = - 1}} =
              left.vphantom{Huge A}-,partiald{}{m}bracks{Gammapars{k - m} over k!,Gammapars{-m}}rightvert_{ m = - 1}
              \[5mm] = &
              -,{1 over k!},
              {-Gamma, 'pars{k + 1}Gammapars{1} + Gamma, 'pars{1}Gammapars{k + 1}over Gamma^{2}pars{1}}
              \[5mm] = &
              -,{1 over k!}bracks{%
              {-Gammapars{k + 1}Psipars{k + 1} +
              Gammapars{1}Psipars{1}Gammapars{k + 1}}}
              \[5mm] = &
              Psipars{k + 1} - Psipars{1} = color{#f00}{H_{k}}
              \[1cm]
              stackrel{mbox{see} eqref{1}}{implies} & ,,,
              bbox[10px,#ffe,border:1px dotted navy]{ds{%
              -,{lnpars{1 - x} over 1 - x} = sum_{k = 1}^{infty}H_{k}, x^{k}}}
              end{align}





              share|cite|improve this answer

























                up vote
                2
                down vote



                accepted







                up vote
                2
                down vote



                accepted






                $newcommand{bbx}[1]{,bbox[8px,border:1px groove navy]{{#1}},}
                newcommand{braces}[1]{leftlbrace,{#1},rightrbrace}
                newcommand{bracks}[1]{leftlbrack,{#1},rightrbrack}
                newcommand{dd}{mathrm{d}}
                newcommand{ds}[1]{displaystyle{#1}}
                newcommand{expo}[1]{,mathrm{e}^{#1},}
                newcommand{ic}{mathrm{i}}
                newcommand{mc}[1]{mathcal{#1}}
                newcommand{mrm}[1]{mathrm{#1}}
                newcommand{pars}[1]{left(,{#1},right)}
                newcommand{partiald}[3]{frac{partial^{#1} #2}{partial #3^{#1}}}
                newcommand{root}[2]{,sqrt[#1]{,{#2},},}
                newcommand{totald}[3]{frac{mathrm{d}^{#1} #2}{mathrm{d} #3^{#1}}}
                newcommand{verts}[1]{leftvert,{#1},rightvert}$

                With the identity
                $ds{pars{1 - x}^{m} = sum_{k = 0}^{infty}
                {m choose k}pars{-x}^{k} =
                sum_{k = 0}^{infty}{k - m - 1 choose k}x^{k}}$
                :




                begin{equation}
                begin{array}{l}
                mbox{Derivative respect of} ds{m}:
                \
                ds{pars{1 - x}^{m}lnpars{1 - x} =
                sum_{k = 0}^{infty}bracks{partiald{}{m}{k - m - 1 choose k}}x^{k}}
                \[5mm]
                mbox{The limit}ds{ m to - 1}:
                \
                ds{-,{lnpars{1 - x} over 1 - x} =
                sum_{k = 0}^{infty}color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}
                _{ m = - 1}} x^{k}}
                end{array}
                label{1}tag{1}
                end{equation}



                begin{align}
                &color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}_{ m = - 1}} =
                left.vphantom{Huge A}-,partiald{}{m}bracks{Gammapars{k - m} over k!,Gammapars{-m}}rightvert_{ m = - 1}
                \[5mm] = &
                -,{1 over k!},
                {-Gamma, 'pars{k + 1}Gammapars{1} + Gamma, 'pars{1}Gammapars{k + 1}over Gamma^{2}pars{1}}
                \[5mm] = &
                -,{1 over k!}bracks{%
                {-Gammapars{k + 1}Psipars{k + 1} +
                Gammapars{1}Psipars{1}Gammapars{k + 1}}}
                \[5mm] = &
                Psipars{k + 1} - Psipars{1} = color{#f00}{H_{k}}
                \[1cm]
                stackrel{mbox{see} eqref{1}}{implies} & ,,,
                bbox[10px,#ffe,border:1px dotted navy]{ds{%
                -,{lnpars{1 - x} over 1 - x} = sum_{k = 1}^{infty}H_{k}, x^{k}}}
                end{align}





                share|cite|improve this answer














                $newcommand{bbx}[1]{,bbox[8px,border:1px groove navy]{{#1}},}
                newcommand{braces}[1]{leftlbrace,{#1},rightrbrace}
                newcommand{bracks}[1]{leftlbrack,{#1},rightrbrack}
                newcommand{dd}{mathrm{d}}
                newcommand{ds}[1]{displaystyle{#1}}
                newcommand{expo}[1]{,mathrm{e}^{#1},}
                newcommand{ic}{mathrm{i}}
                newcommand{mc}[1]{mathcal{#1}}
                newcommand{mrm}[1]{mathrm{#1}}
                newcommand{pars}[1]{left(,{#1},right)}
                newcommand{partiald}[3]{frac{partial^{#1} #2}{partial #3^{#1}}}
                newcommand{root}[2]{,sqrt[#1]{,{#2},},}
                newcommand{totald}[3]{frac{mathrm{d}^{#1} #2}{mathrm{d} #3^{#1}}}
                newcommand{verts}[1]{leftvert,{#1},rightvert}$

                With the identity
                $ds{pars{1 - x}^{m} = sum_{k = 0}^{infty}
                {m choose k}pars{-x}^{k} =
                sum_{k = 0}^{infty}{k - m - 1 choose k}x^{k}}$
                :




                begin{equation}
                begin{array}{l}
                mbox{Derivative respect of} ds{m}:
                \
                ds{pars{1 - x}^{m}lnpars{1 - x} =
                sum_{k = 0}^{infty}bracks{partiald{}{m}{k - m - 1 choose k}}x^{k}}
                \[5mm]
                mbox{The limit}ds{ m to - 1}:
                \
                ds{-,{lnpars{1 - x} over 1 - x} =
                sum_{k = 0}^{infty}color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}
                _{ m = - 1}} x^{k}}
                end{array}
                label{1}tag{1}
                end{equation}



                begin{align}
                &color{#f00}{bracks{-,partiald{}{m}{k - m - 1 choose k}}_{ m = - 1}} =
                left.vphantom{Huge A}-,partiald{}{m}bracks{Gammapars{k - m} over k!,Gammapars{-m}}rightvert_{ m = - 1}
                \[5mm] = &
                -,{1 over k!},
                {-Gamma, 'pars{k + 1}Gammapars{1} + Gamma, 'pars{1}Gammapars{k + 1}over Gamma^{2}pars{1}}
                \[5mm] = &
                -,{1 over k!}bracks{%
                {-Gammapars{k + 1}Psipars{k + 1} +
                Gammapars{1}Psipars{1}Gammapars{k + 1}}}
                \[5mm] = &
                Psipars{k + 1} - Psipars{1} = color{#f00}{H_{k}}
                \[1cm]
                stackrel{mbox{see} eqref{1}}{implies} & ,,,
                bbox[10px,#ffe,border:1px dotted navy]{ds{%
                -,{lnpars{1 - x} over 1 - x} = sum_{k = 1}^{infty}H_{k}, x^{k}}}
                end{align}






                share|cite|improve this answer














                share|cite|improve this answer



                share|cite|improve this answer








                edited Nov 12 at 18:20

























                answered Oct 30 '16 at 17:56









                Felix Marin

                65.8k7107138




                65.8k7107138






















                    up vote
                    3
                    down vote













                    It is useful to notice that multiplication of a series $A(x)=sum_{n=0}^infty a_nx^n$ with the geometric series $frac{1}{1-x}$ transforms the sequence $(a_n)_{ngeq 0}$ to a sequence of sums $left(sum_{k=0}^na_kright)_{ngeq 0}$. We obtain



                    begin{align*}
                    frac{1}{1-x}A(x)&=frac{1}{1-x}sum_{n=0}^infty a_n x^n\
                    &=sum_{n=0}^infty left(sum_{k=0}^n a_kright) x^ntag{1}
                    end{align*}



                    So, it is sufficient to determine the $n$-th coefficient of $A(x)$ in order to also know the $n$-th coefficient of $frac{1}{1-x}A(x)$.




                    Since the series expansion of $-log (1-x)$ is known to be
                    begin{align*}
                    -log(1-x)=sum_{n=1}^infty frac{x^n}{n}qquadqquadqquad |x|<1
                    end{align*}
                    it follows from (1)
                    begin{align*}
                    -frac{log(1-x)}{1-x}&=frac{1}{1-x}sum_{n=1}^infty frac{x^n}{n}
                    =sum_{n=1}^infty left(sum_{k=1}^nfrac{1}{k}right)x^n\
                    &=sum_{n=1}^infty H_nx^n
                    end{align*}







                    share|cite|improve this answer























                    • I probably wrote the question wrong. I actually started off wanting to sum 1+1/2+1/3+... - so I tried generating functions. By formula for nth coeffiecient I meant something like n*(n+1)/2 for 1+2+3+4+...n
                      – Adam
                      Oct 30 '16 at 5:59















                    up vote
                    3
                    down vote













                    It is useful to notice that multiplication of a series $A(x)=sum_{n=0}^infty a_nx^n$ with the geometric series $frac{1}{1-x}$ transforms the sequence $(a_n)_{ngeq 0}$ to a sequence of sums $left(sum_{k=0}^na_kright)_{ngeq 0}$. We obtain



                    begin{align*}
                    frac{1}{1-x}A(x)&=frac{1}{1-x}sum_{n=0}^infty a_n x^n\
                    &=sum_{n=0}^infty left(sum_{k=0}^n a_kright) x^ntag{1}
                    end{align*}



                    So, it is sufficient to determine the $n$-th coefficient of $A(x)$ in order to also know the $n$-th coefficient of $frac{1}{1-x}A(x)$.




                    Since the series expansion of $-log (1-x)$ is known to be
                    begin{align*}
                    -log(1-x)=sum_{n=1}^infty frac{x^n}{n}qquadqquadqquad |x|<1
                    end{align*}
                    it follows from (1)
                    begin{align*}
                    -frac{log(1-x)}{1-x}&=frac{1}{1-x}sum_{n=1}^infty frac{x^n}{n}
                    =sum_{n=1}^infty left(sum_{k=1}^nfrac{1}{k}right)x^n\
                    &=sum_{n=1}^infty H_nx^n
                    end{align*}







                    share|cite|improve this answer























                    • I probably wrote the question wrong. I actually started off wanting to sum 1+1/2+1/3+... - so I tried generating functions. By formula for nth coeffiecient I meant something like n*(n+1)/2 for 1+2+3+4+...n
                      – Adam
                      Oct 30 '16 at 5:59













                    up vote
                    3
                    down vote










                    up vote
                    3
                    down vote









                    It is useful to notice that multiplication of a series $A(x)=sum_{n=0}^infty a_nx^n$ with the geometric series $frac{1}{1-x}$ transforms the sequence $(a_n)_{ngeq 0}$ to a sequence of sums $left(sum_{k=0}^na_kright)_{ngeq 0}$. We obtain



                    begin{align*}
                    frac{1}{1-x}A(x)&=frac{1}{1-x}sum_{n=0}^infty a_n x^n\
                    &=sum_{n=0}^infty left(sum_{k=0}^n a_kright) x^ntag{1}
                    end{align*}



                    So, it is sufficient to determine the $n$-th coefficient of $A(x)$ in order to also know the $n$-th coefficient of $frac{1}{1-x}A(x)$.




                    Since the series expansion of $-log (1-x)$ is known to be
                    begin{align*}
                    -log(1-x)=sum_{n=1}^infty frac{x^n}{n}qquadqquadqquad |x|<1
                    end{align*}
                    it follows from (1)
                    begin{align*}
                    -frac{log(1-x)}{1-x}&=frac{1}{1-x}sum_{n=1}^infty frac{x^n}{n}
                    =sum_{n=1}^infty left(sum_{k=1}^nfrac{1}{k}right)x^n\
                    &=sum_{n=1}^infty H_nx^n
                    end{align*}







                    share|cite|improve this answer














                    It is useful to notice that multiplication of a series $A(x)=sum_{n=0}^infty a_nx^n$ with the geometric series $frac{1}{1-x}$ transforms the sequence $(a_n)_{ngeq 0}$ to a sequence of sums $left(sum_{k=0}^na_kright)_{ngeq 0}$. We obtain



                    begin{align*}
                    frac{1}{1-x}A(x)&=frac{1}{1-x}sum_{n=0}^infty a_n x^n\
                    &=sum_{n=0}^infty left(sum_{k=0}^n a_kright) x^ntag{1}
                    end{align*}



                    So, it is sufficient to determine the $n$-th coefficient of $A(x)$ in order to also know the $n$-th coefficient of $frac{1}{1-x}A(x)$.




                    Since the series expansion of $-log (1-x)$ is known to be
                    begin{align*}
                    -log(1-x)=sum_{n=1}^infty frac{x^n}{n}qquadqquadqquad |x|<1
                    end{align*}
                    it follows from (1)
                    begin{align*}
                    -frac{log(1-x)}{1-x}&=frac{1}{1-x}sum_{n=1}^infty frac{x^n}{n}
                    =sum_{n=1}^infty left(sum_{k=1}^nfrac{1}{k}right)x^n\
                    &=sum_{n=1}^infty H_nx^n
                    end{align*}








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                    edited Oct 29 '16 at 22:44

























                    answered Oct 29 '16 at 22:36









                    Markus Scheuer

                    58.9k454140




                    58.9k454140












                    • I probably wrote the question wrong. I actually started off wanting to sum 1+1/2+1/3+... - so I tried generating functions. By formula for nth coeffiecient I meant something like n*(n+1)/2 for 1+2+3+4+...n
                      – Adam
                      Oct 30 '16 at 5:59


















                    • I probably wrote the question wrong. I actually started off wanting to sum 1+1/2+1/3+... - so I tried generating functions. By formula for nth coeffiecient I meant something like n*(n+1)/2 for 1+2+3+4+...n
                      – Adam
                      Oct 30 '16 at 5:59
















                    I probably wrote the question wrong. I actually started off wanting to sum 1+1/2+1/3+... - so I tried generating functions. By formula for nth coeffiecient I meant something like n*(n+1)/2 for 1+2+3+4+...n
                    – Adam
                    Oct 30 '16 at 5:59




                    I probably wrote the question wrong. I actually started off wanting to sum 1+1/2+1/3+... - so I tried generating functions. By formula for nth coeffiecient I meant something like n*(n+1)/2 for 1+2+3+4+...n
                    – Adam
                    Oct 30 '16 at 5:59


















                     

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