What is the recursive formula for the sequence 8, 10, 12.5, 15.625, …?

Answer 1

You can see that the consecutive numbers don't have constant difference.

Let's look at the ratio

a2/a1 = 10/8 =5/4 = 1.25

a3/a2 =12.5/10 = 1.25

a4/a3 = 15.625/12.5 = 1.25

Clearly f(n) = 1.25 f(n-1) with f(1) =8