English

On subwords in the base-$q$ expansion of polynomial and exponential functions

Number Theory 2017-07-06 v1

Abstract

Let ww be any word over the alphabet {0,1,,q1}\{0,1,\ldots, q-1\}, and denote by hh either a polynomial of degree d1d\geq 1 or h:nmnh: n\mapsto m^n for a fixed mm. Furthermore, denote by eq(w;h(n))e_q(w;h(n)) the number of occurrences of ww as a subword in the base-qq expansion of h(n)h(n). We show that lim supneq(w;h(n))lognγ(w)llogq, \limsup_{n\to\infty} \frac{e_q(w;h(n))}{\log n}\geq \frac{\gamma(w)}{l\log q}, where ll is the length of ww and γ(w)1\gamma(w)\geq 1 is a constant depending on a property of circular shifts of ww. This generalizes work by the second author as well as is related to a generalization of Lagarias of a problem of Erd\H{o}s.

Keywords

Cite

@article{arxiv.1707.01440,
  title  = {On subwords in the base-$q$ expansion of polynomial and exponential functions},
  author = {Hajime Kaneko and Thomas Stoll},
  journal= {arXiv preprint arXiv:1707.01440},
  year   = {2017}
}

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8 pages