Congruences for overpartitions with restricted odd differences

Abstract

In recent work, Bringmann et al. used q-difference equations to compute a two-variable q-hypergeometric generating function for the number of overpartitions where (i) the difference between two successive parts may be odd only if the larger of the two is overlined, and (ii) if the smallest part is odd then it is overlined, given by $\overline{t}(n)$. They also established the two-variable generating function for the same overpartitions where (i) consecutive parts differ by a multiple of $(k+1)$ unless the larger of the two is overlined, and (ii) the smallest part is overlined unless it is divisible by $k+1$, enumerated by $\overline{t}^{(k)}(n)$. As an application they proved that $\overline{t}(n)\equiv 0\pmod {3}$ if n is not a square. In this paper, we extend the study of congruence properties of $\overline{t}(n)$, and we prove congruences modulo 3 and 6 for $\overline{t}(n)$, congruences modulo 2 and 4 for $\overline{t}^{(3)}(n)$ and $\overline{t}^{(7)}(n)$, congruences modulo 4 and 5 for $\overline{t}^{(4)}(n)$, and congruences modulo 3, 6 and 12 for $\overline{t}^{(8)}(n)$.