English

On the Order of $a$ modulo $n$ on Average

Number Theory 2016-05-20 v2

Abstract

Let a>1a>1 be an integer. Denote by la(n)l_a(n) the multiplicative order of aa modulo integer n1n\geq 1. We prove that there is a positive constant δ\delta such that if x1δlog3x=o(y)x^{1-\delta}\log^3 x = o(y), then 1ya<y1xa<n<x(a,n)=1la(n)=xlogxexp(Bloglogxlogloglogx(1+o(1))) \frac1y \sum_{a<y} \frac1x \sum_{\substack{{a<n<x}\\{(a,n)=1}}}l_a(n) = \frac x{\log x}\exp \left(B\frac{\log\log x}{\log\log\log x}(1+o(1))\right) where B=eγp(11(p1)2(p+1)). B=e^{-\gamma}\prod_p \left(1-\frac 1{(p-1)^2(p+1)}\right). This is an improvement over a statement in Kurlberg and Pomerance (see ~\cite{KP}): 1x2a<xa<n<xla(n)=xlogxexp(Bloglogxlogloglogx(1+o(1))).\frac{1}{x^2} \sum_{a<x} \sum_{a<n<x} l_a(n) = \frac x{\log x} \exp \left(B \frac{\log\log x} {\log\log\log x} (1+o(1)) \right).

Keywords

Cite

@article{arxiv.1509.03768,
  title  = {On the Order of $a$ modulo $n$ on Average},
  author = {Sungjin Kim},
  journal= {arXiv preprint arXiv:1509.03768},
  year   = {2016}
}
R2 v1 2026-06-22T10:55:12.643Z