I am trying to code the Fourier expansion of f | T_{p^2} for a
half integer weight modular form but I am getting incorrect type in gtos error.
Here is my code:
S(f, p, k) = {f = truncate(f); sum(n = 1, poldegree(f), (polcoeff(f, (n * p^2))) + (kronecker(-4, n)^(k - (1/2)) * kronecker(12 * n,p) * p^(k - (3/2)) * polcoeff(f, n)) + (sumdiv(n, p, p^((2 * k)- 2) * polcoeff(f, n/p^2))) * q^n) + O(q^(poldegree(f) + 1));}
Here is the actual formula:
f | T_{p^2} = f | U_{p^2} + p^(k - 3/2) (-4/p)^{k - (1/2)} (12/p) (n/p) f + p^{2k - 2} f | V_{p^2}.
I understand mfhecke could work in this setting but I am trying to code a variant
of it and this is one my test cases. Could you please suggest what went wrong with this function S(f,p,k).