On the addition of units and non-units in finite commutative rings

Abstract

Let $R$ be a finite commutative ring. In this paper, we find the number of representations of a fixed member of $R$ to be the sum of $k$ units in $R$, and the sum of $k$ non-units, and as a sum of a unit and a non-unit. We prove that, if $\Z _2$ is not a quotient of $R$, then every $r\in R$ can be written as a sum of $k$ units, for each integer $k > 1$.