English

A series involving a product of four consecutive harmonic numbers

Number Theory 2025-07-29 v1

Abstract

In correspondence with Goldbach, Euler began investigating series of the form k1km(1+2n++kn)\sum_{k \geq 1} k^{-m}\left(1 + 2^{-n} + \cdots + k^{-n}\right), which are known today as Euler sums. For the case where n=1n=1 and m2m \geq 2, Euler was able to obtain a closed form in terms of zeta values. We use elementary techniques in the spirit of Euler to evaluate the series k1HkHk+1Hk+2Hk+3k(k+1)(k+2)(k+3),\sum_{k \geq 1} \frac{H_k H_{k+1} H_{k+2} H_{k+3}}{k(k+1)(k+2)(k+3)}, where Hk:=1+12++1kH_k := 1 + \frac{1}{2} + \cdots + \frac{1}{k} is the kkth harmonic number, in terms of zeta values. The closed form is a potential counterexample to a conjecture of Furdui and S\^int\u{a}m\u{a}rian. We relate this problem to conjectures regarding irrationality and Q\mathbb{Q}-linear independence of zeta values.

Keywords

Cite

@article{arxiv.2507.19502,
  title  = {A series involving a product of four consecutive harmonic numbers},
  author = {Wilson J. Chen and Vincent Nguyen},
  journal= {arXiv preprint arXiv:2507.19502},
  year   = {2025}
}

Comments

10 pages, 27 references