hi there!
first we need to find out how much they are adding to each number to make the next number.
ex: 4 + 4 = 8, 8 + 8 = 16, and so on.
so continuing with 32,
32 + 32 = 64
64 + 64 = 128
128 + 128 = 256
256 + 256 = 512
4, 8, 16, 32, 64, 128, 256, 512
the 8th term of the sequence will be 512
hope this ! ~