I have the following sequence

$\{n^4-6n^2\}$

I have to determine if the sequence is non-decreasing, increasing or decreasing.

In my opinion, the sequence is neither, decreasing, non-decreasing nor increasing because it seems to be increasing for all the terms except for the first and second term. Am I right or I am right?

By the way,is there category for such a sequence? where you have an interval of increasing terms and one of decreasing terms or is such a sequence not even possible?