English

Infinite products involving binary digit sums

Number Theory 2018-05-17 v2

Abstract

Let (un)n0(u_n)_{n\ge 0} denote the Thue-Morse sequence with values ±1\pm 1. The Woods-Robbins identity below and several of its generalisations are well-known in the literature \begin{equation*}\label{WR}\prod_{n=0}^\infty\left(\frac{2n+1}{2n+2}\right)^{u_n}=\frac{1}{\sqrt 2}.\end{equation*} No other such product involving a rational function in nn and the sequence unu_n seems to be known in closed form. To understand these products in detail we study the function \begin{equation*}f(b,c)=\prod_{n=1}^\infty\left(\frac{n+b}{n+c}\right)^{u_n}.\end{equation*} We prove some analytical properties of ff. We also obtain some new identities similar to the Woods-Robbins product.

Keywords

Cite

@article{arxiv.1709.04104,
  title  = {Infinite products involving binary digit sums},
  author = {Samin Riasat},
  journal= {arXiv preprint arXiv:1709.04104},
  year   = {2018}
}

Comments

Accepted in Proc. AMMCS 2017, updated according to the referees' comments

R2 v1 2026-06-22T21:41:11.345Z