input: Write a function to generate a list of all numbers from 0 to 50 that are divisible by both 3 and 5. If no such numbers exist, return an empty list.
  assert div_by_3_and_5()==[0, 15, 30, 45]
  assert div_by_3_and_5()==[0, 15, 30, 45]
  assert div_by_3_and_5()==[0, 15, 30, 45]
  assert div_by_3_and_5()==[0, 15, 30, 45]
  assert div_by_3_and_5()==[0, 15, 30, 45]
output: def div_by_3_and_5():
      return [i for i in range(51) if i % 3 == 0 and i % 5 == 0]