English

Infinite products with strongly $B$-multiplicative exponents

Number Theory 2011-03-29 v2

Abstract

Let N1,B(n)N_{1,B}(n) denote the number of ones in the BB-ary expansion of an integer nn. Woods introduced the infinite product P:=n0(2n+12n+2)(1)N1,2(n)P :=\prod_{n \geq 0} (\frac{2n+1}{2n+2})^{(-1)^{N_{1,2}(n)}} and Robbins proved that P=1/2P = 1/\sqrt{2}. Related products were studied by several authors. We show that a trick for proving that P2=1/2P^2 = 1/2 (knowing that PP converges) can be extended to evaluating new products with (generalized) strongly BB-multiplicative exponents. A simple example is n0(Bn+1Bn+2)(1)N1,B(n)=1B. \prod_{n \geq 0} (\frac{Bn+1}{Bn+2})^{(-1)^{N_{1,B}(n)}} = \frac{1}{\sqrt B}.

Keywords

Cite

@article{arxiv.0709.4031,
  title  = {Infinite products with strongly $B$-multiplicative exponents},
  author = {Jean-Paul Allouche and Jonathan Sondow},
  journal= {arXiv preprint arXiv:0709.4031},
  year   = {2011}
}

Comments

Updated [14] and journal reference

R2 v1 2026-06-21T09:21:51.305Z