input: Write a python function to count numbers larger than a given number.
  assert larger_than_num([1, 3, 5, 7, 9], 4) == 3
  assert larger_than_num([10, 20, 30, 40, 50], 25) == 3
  assert larger_than_num([5, 15, 25, 35, 45], 20) == 3
output: def larger_than_num(lst, num):
      return sum(1 for x in lst if x > num)