Vanishing coefficients in some $q$-series expansions

Abstract

Motivated by the recent work of Hirschhorn on vanishing coefficients of the arithmetic progressions in certain $q$-series expansions, we study some variants of these $q$-series and prove some comparable results. For instance, let \begin{align*} (-q,-q^{4};q^{5})_{\infty}^{2}(q^{4},q^{6};q^{10})_{\infty}=\sum_{n=0}^{\infty}a_{1}(n)q^{n}, \end{align*} then \begin{align*} a_{1}(5n+3)=0. \end{align*}