2 problems

Let $\tau\in\mathfrak{H}$, let $q=e^{2\pi i\tau}$, and let $C_4(\tau)=\sum_{n=1}^{\infty}c(n)q^n$ be the meromorphic modular form on $\Gamma_0(2)$ defined in the source from the no…

Unbounded denominators conjecture. The Fourier coefficients of $f$ have bounded denominators if and only if $f$ is a cusp form for a congruence subgroup.