a(n) = 729*n^2 - 1016*n + 354.

Terms

a(0) =67a(1) =1238a(2) =3867a(3) =7954a(4) =13499a(5) =20502a(6) =28963a(7) =38882a(8) =50259a(9) =63094a(10) =77387a(11) =93138a(12) =110347a(13) =129014a(14) =149139a(15) =170722a(16) =193763a(17) =218262a(18) =244219a(19) =271634a(20) =300507a(21) =330838a(22) =362627a(23) =395874a(24) =430579a(25) =466742a(26) =504363a(27) =543442a(28) =583979a(29) =625974