Improved average and almost-all bounds for $G(n)$

Abstract

In this paper we study the least positive integer $G(n)$ such that the integers $a\le G(n)$ with $(a,n)=1$ generate $(\mathbb{Z}/n\mathbb{Z}{)}^{\times }$. We prove that, for every $\epsilon >0$, \[ \sum_{n\leq x}G(n)\ll_\varepsilon x(\log x)^{8/3+\varepsilon}, \] improving the previously known bound $\ll x(\log x{)}^{97}$. We also prove that $G(n)\le (\log n{)}^2$ for almost all $n$, unconditionally. Thus, for almost all $n$, we obtain the same logarithmic exponent $2$ as in the classical pointwise bound under GRH.