input: Write a python function to find numbers divisible by 3 but not by 7 within a given range.
  assert divisible_by_3_not_7(30, 51) == [30, 33, 36, 39, 42, 45, 48]
  assert divisible_by_3_not_7(20, 40) == [21, 24, 27, 30, 33, 36, 39]
  assert divisible_by_3_not_7(50, 60) == [51, 54, 57]
output: def divisible_by_3_not_7(start, end):
      return [i for i in range(start, end) if i % 3 == 0 and i % 7 != 0]