a(n) = n*(2*n^2 + 5*n + 19)/2.

Terms

a(0) =0a(1) =13a(2) =37a(3) =78a(4) =142a(5) =235a(6) =363a(7) =532a(8) =748a(9) =1017a(10) =1345a(11) =1738a(12) =2202a(13) =2743a(14) =3367a(15) =4080a(16) =4888a(17) =5797a(18) =6813a(19) =7942a(20) =9190a(21) =10563a(22) =12067a(23) =13708a(24) =15492a(25) =17425a(26) =19513a(27) =21762a(28) =24178a(29) =26767