A combinatorial study and comparison of partial theta identities of Andrews and Ramanujan

Abstract

We provide a simple proof of a partial theta identity of Andrews and study the underlying combinatorics. This yields a weighted partition theorem involving partitions into distinct parts with smallest part odd which turns out to be a companion to a weighted partition theorem involving the same partitions that we recently deduced from a partial theta identity in Ramanujan’s Lost Notebook. We also establish some new partition identities from certain special cases of Andrews’ partial theta identity.