Tribaconi

public class Xbonacci {

  public double[] tribonacci(double[] s, int n) {
      double[] ret = new double[n];

      System.arraycopy(s, 0, ret, 0, s.length);

      for (int i = s.length; i < n; i++) {
          ret[i] = 0;

          for (int j = i - 3; j < i; j++)
              ret[i] += j;
      }

      return ret;
  }
}