adding 0 and 0: 0 multiplying 0 and 0: 0 adding 1 and 1: 2 multiplying 1 and 1: 1 adding 2 and 2: 4 multiplying 2 and 2: 4 adding 3 and 3: 6 multiplying 3 and 3: 9 adding 4 and 4: 8 multiplying 4 and 4: 16