Question

If n is a term of the sequence 2, 5, 8, 11, ..., which expression would give the value of n?

2 n + 1
2 n - 1
3 n - 1
n + 3

Answer 1

The sequence is arithmetic with first term 2 and common difference 3. The nth term is

a_n = 2 + (n − 1)·3 = 3n − 1.

So the correct expression is 3n − 1.