Accord.Math.Gamma.Multivariate C# (CSharp) Method

        public static double Multivariate(double x, int p)
        {
            if (p < 1)
                throw new ArgumentOutOfRangeException("p",
                    "Parameter p must be higher than 1.");

            if (p == 1)
                return Function(x);


            double prod = Math.Pow(Math.PI, (1 / 4.0) * p * (p - 1));

            for (int i = 0; i < p; i++)
                prod *= Function(x - 0.5 * i);

            return prod;
        }