recursion.dart

void main() {
  print(factorial(1));
  print(factorial(5));
  print(factorial(10));
  print(factorial(20));
}

int factorial(int n) {
  if (n <= 1) { // Base case
    return 1;
  } else {      // Recursive case/call
    return (n * factorial(n - 1));
  }
}