An observation on factorizations of finite groups

Abstract

Given a finite group $G$ and a factorization of its order, $|G|= a_1 a_2,$ we show that a sufficient condition for there to exist subsets $A_1,\,A_2\subseteq G$ such that $|A_1| = a_1,$ $|A_2| = a_2,$ and $G = A_1\,A_2,$ is that there exist a chain of subgroups $\{e\} = G_0 < \dots < G_n = G$ such that $a_1$ is the product of some subfamily of the indices $|G_i:G_{i-1}|$ (and hence $a_2$ is the product of the complementary subfamily).