a(n) = n*(n^2 + 3)/2.

Terms

a(0) =0a(1) =2a(2) =7a(3) =18a(4) =38a(5) =70a(6) =117a(7) =182a(8) =268a(9) =378a(10) =515a(11) =682a(12) =882a(13) =1118a(14) =1393a(15) =1710a(16) =2072a(17) =2482a(18) =2943a(19) =3458a(20) =4030a(21) =4662a(22) =5357a(23) =6118a(24) =6948a(25) =7850a(26) =8827a(27) =9882a(28) =11018a(29) =12238