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+# 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) ...
+