What are the multiples of 16 and 18?

First, factor:

16 = 2*2*2*2

18 = 2*3*3

Multiply the factors (only count overlapping ones once) to find the least common multiple (LCM)

LCM = 2*2*2*2*3*3 = 144

The multiples of 16 and 18 are {144, 288, 432, 576...}