Given the arithmetic sequence an = 3 + 2(n − 1), what is the domain for n?

The set of all positive integers equal to or greater than 1

Step-by-step 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.