a(n) = (9*n^4 + 4*n^3 - n)/2.

Terms

a(0) =0a(1) =6a(2) =87a(3) =417a(4) =1278a(5) =3060a(6) =6261a(7) =11487a(8) =19452a(9) =30978a(10) =46995a(11) =68541a(12) =96762a(13) =132912a(14) =178353a(15) =234555a(16) =303096a(17) =385662a(18) =484047a(19) =600153a(20) =735990a(21) =893676a(22) =1075437a(23) =1283607a(24) =1520628a(25) =1789050a(26) =2091531a(27) =2430837a(28) =2809842a(29) =3231528