Question

Given the geometric sequence where a1 = 2 and the common ratio is 4, what is the domain for n?

All real numbers
All integers where n ≥ 0
All integers where n ≥ 1
All integers where n ≥ 2

Answer 1

by definition, a sequence is a function from the set of natural number to a subset of real number:
\[\Large n \to {a_n},\quad \mathbb{N} \to \mathbb{R}\]
in your case it is \[\Large n \geqslant 1\]