function Lanczos_Gamma(num)   
    {  
      var p = [  
        0.99999999999980993, 676.5203681218851, -1259.1392167224028,  
        771.32342877765313, -176.61502916214059, 12.507343278686905, -0.13857109526572012, 9.9843695780195716e-6, 1.5056327351493116e-7  
      ];  
      var i;  
      var g = 7;  
      if (num < 0.5) return Math.PI / (Math.sin(Math.PI * num) * calculus.LanczosGamma(1 - num));  
      num -= 1;  
      var a = p[0];  
      var t = num + g + 0.5;  
      for (i = 1; i < p.length; i++) {  
        a += p[i] / (num + i);  
      }  
      return Math.sqrt(2 * Math.PI) * Math.pow(t, num + 0.5) * Math.exp(-t) * a;  
    }  
    console.log(Lanczos_Gamma(5));