# https://en.wikipedia.org/wiki/Sterling_Approximation
# An alternative approximation for the Gamma function stated by Srinivasa
# Ramanujan (Ramanujan 1988) is

    Gamma(1+x) ~= sqrt(pi)((x/e)^x)(8x^3 + 4x^2 + x + 1/30)^(1/6)

# for x >= 0. The equivalent approximation for ln(n!) has an asymptotic error
# of 1/(1400*n^3) ...