The sum to n terms of the series 22+42+62+..........is
22+42+62+..........+(2n)2
= (2)2(12+22+32+......+n2)
= 4n(n+1)(2n+1)6 = 2n(n+1)(2n+1)3 .
The sum of n terms of the series 22+42+62+..........is