What is the next number of the following sequence - .5, 2, 6.5, 20, ??

Answer 1

Here is the solution (mind boggling) :

.5 = 1/2
next number = (previous numerator * 3 + 1) / 2
Applying the above:
(1 * 3 + 1)/2  = 4/2      ====> 2
(4 * 3 + 1)/2  = 13/2     ====> 6.5
(13 * 3 + 1)/2 = 40/2     ====> 20
(40 * 3 + 1)/2 = 121/2    ====> 60.5

Ans  : 60.5 is the next number.

Answer 2

.5*3 + .5 = 2
2*3 + .5 = 6.5
6.5*3 + .5 = 20
20*3 + .5 = 60.5

Ans :- 60.5