Eta product for mf.15.2.1.a (awaiting review)

This cusp form can be expressed as an eta product $\eta(z)\eta(3z)\eta(5z)\eta(15z)=q\prod_{n=1}^\infty(1-q^n)(1-q^{3n})(1-q^{5n})(1-q^{15n})$, where $q=e^{2\pi iz}$.