| Description: | Calculates the digamma function for any positive integers and multiples of 1/2 (such as 3/2, 5/2, 7/2, etc) using the formulas: ψ(1/2) = -γ – ln 4 = -1.963510026, ψ(1) = -γ = -0.5772156649, ψ(n) = Σ(1/x, x, 1, n-1) - γ for n is an integer, and ψ(n) = Σ(2/(2*x+1), x, 0, n-3/2) - γ – ln 4 for n a multiple of 1/2 for the form p/2, p is odd, where γ = 0.577215664901533 (Euler-Mascheroni constant) |