Answer:
The set of all positive integers equal to or greater than 1
Explanation:
n can take on the integer values 1 ... ∞
The formula for the nth term is a(n) = a(1) + 2(n - 1)
First term: n = 1. Then a(1) = 3 + 2(0) = 3 (as expected).
5th term: n = 5. Then a(5) = 3 + 2(5 - 1) = 3 + 8 = 11
...
and so on.