There are a couple of ways one could approach this. The goal is to find out the factor by which the numbers are increasing. Looking at going from 8 -> 16, we have either added 8, or doubled 8. So the factor is either +8 or x2. Going from 16 -> 32, adding 8 no longer holds true, while multiplying by 2 (doubling 16) does. To confirm what we have found, we can further check our math by using the final two numbers, 32 -> 64, to confirm that the sequence pattern is to double the current number to achieve the next number.
Working backwards, we can half each number to find out the first two numbers in the sequence. 64/2 = 32, 32/2 = 16, 16/2 = 8, 8/2 = 4, 4/2 = 2
