Calculate 2 + 4 + 6 +.. + (2n + 4)

Calculate 2 + 4 + 6 +.. + (2n + 4)

(2+4+6+…… +2n)+(2n+2)+(2n+4)
=2(1+2+3+…… +n)+(4n+6)
=2*n*(n+1)/2+(4n+6)
=n^2 +5n +6