What should come in place of the question mark (?) in the following number series?
4, 15, 16, ?, 36, 63, 64
(a) 25 (b) 30 (c) 32 (d) 35 (e) of these
(d) Pattern is 22, 42 – 1,42 , 62 – 1, 62 and so on.
