a(n) = n*(5*n^2 - 2)/3.

Terms

a(0) =0a(1) =1a(2) =12a(3) =43a(4) =104a(5) =205a(6) =356a(7) =567a(8) =848a(9) =1209a(10) =1660a(11) =2211a(12) =2872a(13) =3653a(14) =4564a(15) =5615a(16) =6816a(17) =8177a(18) =9708a(19) =11419a(20) =13320a(21) =15421a(22) =17732a(23) =20263a(24) =23024a(25) =26025a(26) =29276a(27) =32787a(28) =36568a(29) =40629