PartialSums.java

package alioth.java;

import java.lang.Math;

public class PartialSums {

   static final double twothirds = 2.0/3.0;

   public static void main(String[] args){
      int n = Integer.parseInt(args[0]);

      double a1 = 0.0, a2 = 0.0, a3 = 0.0, a4 = 0.0, a5 = 0.0;
      double a6 = 0.0, a7 = 0.0, a8 = 0.0, a9 = 0.0, alt = -1.0;

      for (int k=1; k<=n; k++){
         double k2 = (double)k * (double)k, k3 = k2 * (double)k;
         double sk = Math.sin(k), ck = Math.cos(k);
         alt = -alt;

         a1 += Math.pow(twothirds,k-1);
         a2 += 1.0/Math.sqrt(k);
         a3 += 1.0/(k*(k+1.0));
         a4 += 1.0/(k3 * sk*sk);
         a5 += 1.0/(k3 * ck*ck);
         a6 += 1.0/k;
         a7 += 1.0/k2;
         a8 += alt/k;
         a9 += alt/(2.0*k -1.0);
      }
      System.out.printf("%.9f\t(2/3)^k\n", a1);
      System.out.printf("%.9f\tk^-0.5\n", a2);
      System.out.printf("%.9f\t1/k(k+1)\n", a3);
      System.out.printf("%.9f\tFlint Hills\n", a4);
      System.out.printf("%.9f\tCookson Hills\n", a5);
      System.out.printf("%.9f\tHarmonic\n", a6);
      System.out.printf("%.9f\tRiemann Zeta\n", a7);
      System.out.printf("%.9f\tAlternating Harmonic\n", a8);
      System.out.printf("%.9f\tGregory\n", a9);
   }
}