void setup() {
  double e = 0;
  long factorial = 1;
  int iterations = 11;
  for (int i = 0; i < iterations; i++) {
    e += (double) (2 * i + 1) / factorial;
    factorial *= (2 * i + 1) * (2 * i + 2);
  }
  println("After " + iterations + " iterations");
  println("Computed value: " + e);
  println("Real value: " + Math.E);
  println("Error: " + (e - Math.E));

  iterations = 21;
  for (int i = 11; i < iterations; i++) {
    e += (double) (2 * i + 1) / factorial;
    factorial *= (2 * i + 1) * (2 * i + 2);
  }
  println("After " + iterations + " iterations");
  println("Computed value: " + e);
  println("Real value: " + Math.E);
  println("Error: " + (e - Math.E));
}