input: Write a python function to generate a multiplication table.
  assert multiplication_table(3) == [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
  assert multiplication_table(2) == [[1, 2], [3, 4]]
  assert multiplication_table(1) == [[1]]
output: def multiplication_table(n):
      return [[i * n + j + 1 for j in range(n)] for i in range(n)]