\[1+\sum_{n=1}^{\infty}\frac{q^{n^{2}+n}}{(1-q)(1-q^{2})\cdots(1-q^{n})}=\prod_{%
n=0}^{\infty}\frac{1}{(1-q^{5n+2})(1-q^{5n+3})}.\]