an = ar^ (n- 1)
for n = 3 (3rd term)
r = common ratio = 4/ 2 = 2
a3 = 2 (2) ^ (3-1)
a3 = 2 (2)^2
a3 = 2 (4)
a3 = 8
n= 4 (4th term)
a4 = 2 (2)^(4-1)
a4 = 2 (2)^3
a4 = 2 (8)
a4 = 16
2, 4 , 8 , 16
