English

An Extension of a Congruence by Tauraso

Number Theory 2018-04-10 v1

Abstract

For a positive integer nn let Hn=k=1n1/nH_n=\sum_{k=1}^{n}1/n be the nnth harmonic number. In this note we prove that for any prime p7p\ge 7, k=1p1Hkk2k=1p1Hk2k32pk=1p11k2(modp2). \sum_{k=1}^{p-1}\frac{H_k}{k^2}\equiv \sum_{k=1}^{p-1}\frac{H_k^2}{k} \equiv\frac{3}{2p}\sum_{k=1}^{p-1}\frac{1}{k^2}\pmod{p^2}. Notice that the first part of this congruence is recently proposed by R. Tauraso as a problem in Amer. Math. Monthly. In our elementary proof of the second part of the above congruence we use certain classical congruences modulo a prime and the square of a prime, some congruences involving harmonic numbers and a combinatorial identity due to V. Hern\'{a}ndez.

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Cite

@article{arxiv.1109.3155,
  title  = {An Extension of a Congruence by Tauraso},
  author = {Romeo Mestrovic},
  journal= {arXiv preprint arXiv:1109.3155},
  year   = {2018}
}

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13 pages