Answer
Not an arithmetic sequence.
Work Step by Step
In order for a sequence to be arithmetic, the difference of all consecutive terms must be constant.
Here: $a_2-a_1=-1-1=-2$
$a_3-a_2=2-(-1)=3$
$a_4-a_3=-2-2=-4$
Thus we can see that the difference is not constant, thus it is not an arithmetic sequence.