Legendre theorems for subclasses of overpartitions

Abstract

A.M. Legendre noted that Euler's pentagonal number theorem implies that the number of partitions of n into an even number of distinct parts almost always equals the number of partitions of n into an odd number of distinct parts (the exceptions occur when n is a pentagonal number). Subsequently other classes of partitions, including overpartitions, have yielded related Legendre theorems. In this paper, we examine four subclasses of overpartitions that have surprising Legendre theorems.