This is a geometric sequence.
Each new term is found by multiplying the last term by 2
1*2 = 2
2*2 = 4
2*4 = 8
2*8 = 16
and so on
Therefore the common ratio is r = 2.
The starting term is a = 1
The general nth term is
where n is an integer (aka whole number) and n starts at n = 1.