Code and computed values for the vanishing of eta^11 modulo 13 along quadratic residue classes

Measures how often the Fourier coefficients of eta^11 vanish modulo 13, and how that frequency depends on quadratic residue classes. Computes a(m) mod 13 for all m <= 10^10, measures the excess density of vanishing along squarefree kernels and its cumulative count exponent, and the factorisation of the Legendre-class dependence over 2260 auxiliary primes. Includes independent reimplementations, structural invariants, and a negative result for the Shimura lift at every level dividing 288.