Java Pyramid

public class Pattern {
      public static void main(String[] args) {

        int a[][]=new int[15][15];
        int num = 25 ;

        for(int i = 0; i < 5; i++){
               for (int k = num - 2 * i; k >= 0; k--)
                     System.out.print(" ");
               for (int j = 0; j <= i; j++) {
                     if (j == 0 || i == j) {
                         a[i][j] = 1;
                     }
                     else {
                         a[i][j] = a[i - 1][j - 1] + a[i - 1][j];
                     }
                      System.out.printf("%4d", a[i][j]);
               }
                System.out.println();
         }
     }
}