void setup() {
  println("First 25 abundant odd numbers: ");
  int abundant = 0;
  int i = 1;
  while (abundant < 25) {
    int sigma_sum = sigma(i);
    if (sigma_sum > 2 * i) {
      abundant++;
      println(i + "  Sigma sum: " + sigma_sum);
    }
    i += 2;
  }
  println("Thousandth abundant odd number: ");
  while (abundant < 1000) {
    int sigma_sum = sigma(i);
    if (sigma_sum > 2 * i) {
      abundant++;
      if (abundant == 1000) {
        println(i + "  Sigma sum: " + sigma_sum);
      }
    }
    i += 2;
  }
  println("First abundant odd number greater than 10^9: ");
  i = int(pow(10, 9)) + 1;
  while (!(sigma(i) > 2 * i)) {
    i += 2;
  }
  println(i + "  Sigma sum: " + sigma(i));
}

int sigma(int n) {
  int sum = 0;
  for (int i = 1; i < sqrt(n); i++) {
    if (n % i == 0) {
      sum += i + n / i;
    }
  }
  if (sqrt(n) % 1 == 0) {
    sum += sqrt(n);
  }
  return sum;
}