a(n) = n*(2*n^2 + n + 1)/2.

Terms

a(0) =2a(1) =11a(2) =33a(3) =74a(4) =140a(5) =237a(6) =371a(7) =548a(8) =774a(9) =1055a(10) =1397a(11) =1806a(12) =2288a(13) =2849a(14) =3495a(15) =4232a(16) =5066a(17) =6003a(18) =7049a(19) =8210a(20) =9492a(21) =10901a(22) =12443a(23) =14124a(24) =15950a(25) =17927a(26) =20061a(27) =22358a(28) =24824a(29) =27465