Answer
It is not an arithmetic sequence.
Work Step by Step
A sequence is arithmetic if $a_2−a_1=a_3−a_2=a_4−a_3=a_5−a_4=...=d$
For the given sequence we have that:
$a_2-a_1=2^2-1^2=4-1=3$
$a_3-a_2=3^2-2^2=9-4=5$
It is not an arithmetic sequence.
