{ "id": "1907.07572", "version": "v1", "published": "2019-07-17T15:14:40.000Z", "updated": "2019-07-17T15:14:40.000Z", "title": "Automatic sequences defined by Theta functions and some infinite products", "authors": [ "Shuo Li" ], "categories": [ "math.NT", "math.CO" ], "abstract": "Let $p(x) \\in C(x)$ be a rational function satisfying the condition $p(0)=1$ and $q$ an integer larger than $1$, in this article we will consider the power expansion of the infinite product $$f(x)=\\prod_{s=0}^{\\infty}f(x^{q^{s}})=\\sum_{i=0}^{\\infty}c_ix^i,$$ and study when the sequence $(c_i)_{i \\in \\mathbf{N}}$ is $q$-automatic. The main result is that for given integers $q \\geq 2$ and $d \\geq 0$, there exist finitely many polynomials of degree $d$ defined over the field of rational numbers $\\mathbf{Q}$, such that $\\prod_{s=0}^{\\infty}f(x^{q^{s}})=\\sum_{i=1}^{\\infty}c_ix^i$ is a $q$-automatic power series.", "revisions": [ { "version": "v1", "updated": "2019-07-17T15:14:40.000Z" } ], "analyses": { "keywords": [ "infinite product", "theta functions", "automatic sequences", "automatic power series", "integer larger" ], "note": { "typesetting": "TeX", "pages": 0, "language": "en", "license": "arXiv", "status": "editable" } } }