int terme_fibo(triangle tr, int ordre, int k) {
  int i, j, terme=0;

  if (k == 1) {
    return 1;
  }
  else if (k % 2 == 0) {
    j=k-1;
    for (i=(k-1); i >= k/2; i--) {
      terme += tr[i][j];
      j -= 2;
    }
    return terme;
  }
  else {
    j=0;
    for (i=(k/2); i<=(k/2)*2; i++) {
      terme += tr[i][j];
      j += 2;
    }
    return terme;
  }
}