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

Terms

a(0) =1a(1) =13a(2) =42a(3) =94a(4) =175a(5) =291a(6) =448a(7) =652a(8) =909a(9) =1225a(10) =1606a(11) =2058a(12) =2587a(13) =3199a(14) =3900a(15) =4696a(16) =5593a(17) =6597a(18) =7714a(19) =8950a(20) =10311a(21) =11803a(22) =13432a(23) =15204a(24) =17125a(25) =19201a(26) =21438a(27) =23842a(28) =26419a(29) =29175