input: Write a python function to calculate the sum of the fourth powers of the first n odd numbers.
  assert odd_num_sum(2) == 82
  assert odd_num_sum(3) == 707
  assert odd_num_sum(4) == 3108
output: def odd_num_sum(n):
      return sum((2 * i + 1) ** 4 for i in range(n))