input: Write a python function to return a list of multiples of 7 up to a given number.
  assert multiplesOf7(20) == [7, 14]
  assert multiplesOf7(50) == [7, 14, 21, 28, 35, 42, 49]
  assert multiplesOf7(7) == [7]
output: def multiplesOf7(n):
      return [i for i in range(7, n+1, 7)]