A generalization of a result on the sum of element orders of a finite group

Abstract

Let $G$ be a finite group and let $\psi (G)$ denote the sum of element orders of $G$. It is well-known that the maximum value of $\phi$ on the set of groups of order $n$, where $n$ is a positive integer, will occur at the cyclic group $C_n$. For nilpotent groups, we prove a natural generalization of this result, obtained by replacing the element orders of $G$ with the element orders relative to a certain subgroup $H$ of $G$.