Find the 4th term

you in advance

So you start off with the given information:
= 2
= ()² + 1

Since you're looking for the 4th term, that would mean that you are looking for .
Since you know that we are looking for when n = 4, you can start with what we started off with, which is n = 1, to get to where n = 4.
When n = 1, b = 2,
when n = 2, b = 3,
when n = 3, b = 4,
when n = 4, b = 5.

So the fourth term, when n = 4, is 5.