Accord.Math.PerlinNoise.Noise C# (CSharp) Method

        private static double Noise(int x)
        {
            int n = (x << 13) ^ x;

            return (1.0 - ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0);
        }