a(n) = n*(7*n^2 + 15*n + 8)/6.

Terms

a(0) =0a(1) =5a(2) =22a(3) =58a(4) =120a(5) =215a(6) =350a(7) =532a(8) =768a(9) =1065a(10) =1430a(11) =1870a(12) =2392a(13) =3003a(14) =3710a(15) =4520a(16) =5440a(17) =6477a(18) =7638a(19) =8930a(20) =10360a(21) =11935a(22) =13662a(23) =15548a(24) =17600a(25) =19825a(26) =22230a(27) =24822a(28) =27608a(29) =30595