Arithmetic properties and asymptotic formulae for $σ_o\text{mex}(n)$ and $σ_e\text{mex}(n)$

Abstract

The minimal excludant of an integer partition is the least positive integer missing from the partition. Let $σ_o\text{mex}(n)$ (resp., $σ_e\text{mex}(n)$) denote the sum of odd (resp., even) minimal excludants over all the partitions of $n$. Recently, Baruah et al. proved a few congruences for these partition functions modulo $4$ and $8$, and asked for asymptotic formulae for the same. In this article, we study the lacunarity of $σ_o\text{mex}(n)$ and $σ_e\text{mex}(n)$ modulo arbitrary powers of $2$ and also prove some infinite families of congruences for $σ_o\text{mex}(n)$ and $σ_e\text{mex}(n)$ modulo $4$ and $8$. We also obtain Hardy-Ramanujan type asymptotic formulae for both $σ_o\text{mex}(n)$ and $σ_e\text{mex}(n)$.