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:
$a_2-a_1=2-1$
$a_3-a_2=4-2=2$
It is not an arithmetic sequence.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.