Minimal zero-sum sequences of length four over cyclic group with order.

Abstract: Let G be a finite cyclic group. Every sequence S over G can be written in the form where and , and the index ind S of S is defined to be the minimum of over all possible such that . A conjecture says that if G is finite such that , then for every minimal zero-sum sequence S. In this paper, we prove that the conjecture holds if has two prime factors. [Copyright &y& Elsevier]