English

Reciprocal Hyperbolic Series of Ramanujan Type

Number Theory 2024-09-27 v6

Abstract

This paper presents an approach to summing a few families of infinite series involving hyperbolic functions, some of which were first studied by Ramanujan. The key idea is based on their contour integral representations and residue computations with the help of some well-known results of Eisenstein series given by Ramanujan, Berndt et al. As our main results, several series involving hyperbolic functions are evaluated and expressed in terms of z=2F1(1/2,1/2;1;x)z={}_2F_1(1/2,1/2;1;x) and z=dz/dxz'=dz/dx. When a certain parameter in these series is equal to π\pi the series are expressed in closed forms in terms of some special values of the Gamma function. Moreover, many new illustrative examples are presented.

Keywords

Cite

@article{arxiv.1801.07565,
  title  = {Reciprocal Hyperbolic Series of Ramanujan Type},
  author = {Ce Xu and Jianqiang Zhao},
  journal= {arXiv preprint arXiv:1801.07565},
  year   = {2024}
}

Comments

29 pages; title changed to reflect the content the paper more precisely; some typos are corrected

R2 v1 2026-06-22T23:53:06.593Z