a(n) = (2*n^3 + 5*n^2 - 11*n)/2.

Terms

a(0) =-2a(1) =7a(2) =33a(3) =82a(4) =160a(5) =273a(6) =427a(7) =628a(8) =882a(9) =1195a(10) =1573a(11) =2022a(12) =2548a(13) =3157a(14) =3855a(15) =4648a(16) =5542a(17) =6543a(18) =7657a(19) =8890a(20) =10248a(21) =11737a(22) =13363a(23) =15132a(24) =17050a(25) =19123a(26) =21357a(27) =23758a(28) =26332a(29) =29085