Here you can find the source of gamma(int alpha)
public static double gamma(int alpha)
//package com.java2s; //License from project: Open Source License public class Main { public static double gamma(int alpha) { return factorial(alpha - 1); }/* w w w. ja v a 2 s.c om*/ public static double factorial(int val) { double result = 1.0; for (int i = 2; i <= val; i++) { result *= i; } return result; } }