PLEASE ANSWER QUICK!!!

The formula for any geometric sequence is a, a, where a, represents the value of the nth term, a, represents the value of the first term, rrepresents the common ratio, and represents the term number. What is the formula for the geometric sequence 4, 8, 16, 32....?
an=4•(1/2)n - 1
an=2•4n-1
an=32•2n-1
an=4•2n-1​