Answer
$n(n+1)$
Work Step by Step
There is a constant difference, 2, between terms.
The terms of the sum
are the first n terms of an arithmetic sequence, $a_{1}=2, d=2.$
Sum of the First $n$ Terms of an arithmetic sequence:
$S_{n}=\displaystyle \frac{n}{2}\left(a_{1}+a_{n}\right)$
$=\displaystyle \frac{n}{2}(2+2n)$
$=\displaystyle \frac{n}{2}\cdot 2(1+n)$
$=n(n+1)$