An entry of Ramanujan on hypergeometric series in his Notebooks (Q1765258)

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An entry of Ramanujan on hypergeometric series in his Notebooks
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    An entry of Ramanujan on hypergeometric series in his Notebooks (English)
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    23 February 2005
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    In this paper the authors provide a proof of a summation formula for a \(_{3}F_{2}\) generalized hypergeometric series at unit argument. Specifically, let \(N\) be a non-negative integer and \(a\) be a complex number which is not a negative integer. If \(\text{Re}\,x< N+2\), then \[ _{3}F_{2}\left[\begin{matrix} a,\,a,\,x\\ a+1,\,a+N+1 \end{matrix};\,1 \right] \] \[ = \frac{a\Gamma(a+N+1)\Gamma(1-x)}{N!\Gamma(a-x+1)}\,(\psi(a-x+1)-\psi(a)-\psi(N+1)-\gamma) \] \[ -\frac{a\Gamma(a+N+1)\Gamma(1-x)}{N!\Gamma(a-x+1)}\sum_{k=1}^{N}\frac{(a)_{k}(-N)_{k}}{k\,.\,k!(a-x+1)_{k}}, \] where \(\psi(x)\) is the digamma function and \(\gamma\) is the Euler constant. This is a more general form of a formula discovered by Ramanujan in Example 7, after Entry 43, in Chapter XII, in his first Notebook. Several remarks regarding special cases of this formula are made.
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    hypergeometric functions
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    Summation theorems
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    Ramanujan Notebooks
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    Gamma and digamma functions
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