Combinatorial proof of an inequality on some partitions separated by parity

Abstract

In 2019, Andrews investigated integer partitions in which all parts of a given parity are smaller than those of the opposite parity and introduced eight partition functions based on the parity of the smaller parts and parts of a given parity appearing at most once or an unlimited number of times. Recently, Bringmann, Craig and Nazaroglu studied the asymptotic behavior of the eight partition functions proved several inequalities for sufficiently large $n$. At the end of their paper, they asked for combinatorial proofs of those inequalities. In this paper, we prove that an inequality on partitions separated by parity holds for $n\ge 373$ by a combinatorial method. This answers a question posed by Bringmann, Craig and Nazaroglu.