Each number goes up by multiplying by 2. For example, the 1 got to 2 by 1 x 2 and 2 got to 4 by 2 x 2 = 4. You would continue this pattern by doing 8 x 2 = 16 for the first blank. 16 x 2 = 32 for the second blank 32 x 2 = 64 for the third blank 64 x 2 = 128 to check your work.
So the answer would be: 1, 2, 4, 8, 16, 32, 64, 128
