Additive and subtractive bases of ${\mathbb{Z}}_m$ in average

Guangping Liang, Yu Zhang, Haode Zuo

Given a positive integer $m$, let ${\mathbb{Z}}_m$ be the set of residue classes mod $m$. For $A\subseteq {\mathbb{Z}}_m$ and $n\in {\mathbb{Z}}_m$, let ${\sigma }_A(n)$ be the number of solutio…