Cohen's prodeulerrat works like magic -- very fast and accurate. Is it possible to extend this to rational products over primes in fixed residue classes? Alternatively, is there some good way to compute this sort of product in PARI/GP?
For example, the product over primes p = 1 (mod 3) of 1/(1 - 1/p^2), or the product over p = a (mod 24) of 1 - f(a)/p^2 where f(a) is in {0, 2, 4, 6} as in