The formula for any geometric sequence is an = a1 · rn - 1 , where an represents the value of the nth term, a1 represents the value of the first term, r represents the common ratio, and n represents the term number. What is the formula for the geometric sequence 4, 8, 16, 32, ...? an = 32 · 2 n - 1 an = 2 · 4 n - 1 an = 4 · 2 n - 1 an = 4 · ( 1/2 ) n - 1