In a geometric sequence, the 23rd term is 16 and the 24th term is 1/4. What is the 30th term?
r = (1/4) / 16 = 1 / 64
30th term =
(1/4)r^6
(1/4) (1/ 64)^6 =
(1/2)^2 * ( 1/ 2^6)^6 =
(1/2^2) * ( 1/2^36) =
1/ 2^38
1 / 274877906944
+834 
