a(n) = n*(4*n^2 + n - 1)/2.

Terms

a(0) =2a(1) =17a(2) =57a(3) =134a(4) =260a(5) =447a(6) =707a(7) =1052a(8) =1494a(9) =2045a(10) =2717a(11) =3522a(12) =4472a(13) =5579a(14) =6855a(15) =8312a(16) =9962a(17) =11817a(18) =13889a(19) =16190a(20) =18732a(21) =21527a(22) =24587a(23) =27924a(24) =31550a(25) =35477a(26) =39717a(27) =44282a(28) =49184a(29) =54435