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arXiv · 2002.03650

On two congruences involving Franel numbers

Ji-Cai Liu
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Abstract

Via symbolic summation method, we establish the following series for $\pi^2$: \begin{align*} \sum_{k=1}^\infty \frac{H_k-2H_{2k}}{(-3)^k k} = \frac{\pi^2}{18}, \end{align*} where $H_k=\sum_{j=1}^k 1/j$. We also derive a $p$-adic congruence related to this series. As an application, we prove two congruences involving Franel numbers, one of which was originally conjectured by Sun.

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Ji-Cai Liu. 2020-02-10. On two congruences involving Franel numbers. https://arxiv.org/abs/2002.03650

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