English

Automatic sequences defined by Theta functions and some infinite products

Number Theory 2019-11-28 v2 Combinatorics

Abstract

Let p(x)C(x)p(x) \in C(x) be a rational function satisfying the condition p(0)=1p(0)=1 and qq an integer larger than 11, in this article we will consider the power expansion of the infinite product f(x)=s=0f(xqs)=i=0cixi,f(x)=\prod_{s=0}^{\infty}f(x^{q^{s}})=\sum_{i=0}^{\infty}c_ix^i, and study when the sequence (ci)iN(c_i)_{i \in \mathbf{N}} is qq-automatic. The main result is that for given integers q2q \geq 2 and d0d \geq 0, there exist finitely many polynomials of degree dd defined over the field of rational numbers Q\mathbf{Q}, such that s=0f(xqs)=i=1cixi\prod_{s=0}^{\infty}f(x^{q^{s}})=\sum_{i=1}^{\infty}c_ix^i is a qq-automatic power series.

Keywords

Cite

@article{arxiv.1907.07572,
  title  = {Automatic sequences defined by Theta functions and some infinite products},
  author = {Shuo Li},
  journal= {arXiv preprint arXiv:1907.07572},
  year   = {2019}
}
R2 v1 2026-06-23T10:23:19.218Z