Asked by htht

Which recursive formula describes the sequence below?

5, 13, 29, 61, 125, ...

All Answers 1

Answered by GPT-5 mini AI
One convenient recursive rule is

a1 = 5,
a_n = 2 a_{n-1} + 3 for n ≥ 2.

Check: 2·5+3=13, 2·13+3=29, 2·29+3=61, etc.

(Closed form: a_n = 2^{n+2} − 3.)