title: Double Factorial 1
signature: doubleFactorial1 :: Integer -> Integer
  doubleFactorial1 n = 
source_py: def double_factorial_1(n):
      res = 1
      for i in range(n, (- 1), (- 2)):
          if ((i == 0) or (i == 1)):
              return res
          else:
              res *= i
source_cpp: unsigned int double_factorial_1(unsigned int n) {
    int res = 1;
    for ( int i = n;
    i >= 0;
    i = i - 2 ) {
      if ( i == 0 || i == 1 ) return res;
      else res *= i;
    }
  }