Accord.Math.Gamma.Stirling C# (CSharp) Метод

        public static double Stirling(double x)
        {
            double MAXSTIR = 143.01608;

            double w = 1.0 / x;
            double y = Math.Exp(x);

            w = 1.0 + w * Special.Polevl(w, STIR, 4);

            if (x > MAXSTIR)
            {
                double v = Math.Pow(x, 0.5 * x - 0.25);

                if (Double.IsPositiveInfinity(v) && Double.IsPositiveInfinity(y))
                {
                    // lim x -> inf { (x^(0.5*x - 0.25)) * (x^(0.5*x - 0.25) / exp(x))  }
                    y = Double.PositiveInfinity;
                }
                else
                {
                    y = v * (v / y);
                }
            }
            else
            {
                y = System.Math.Pow(x, x - 0.5) / y;
            }

            y = Constants.Sqrt2PI * y * w;
            return y;
        }