a(n) = 4*n^3 - 18*n^2 + 27*n - 12.

Terms

a(0) =1a(1) =2a(2) =15a(3) =64a(4) =173a(5) =366a(6) =667a(7) =1100a(8) =1689a(9) =2458a(10) =3431a(11) =4632a(12) =6085a(13) =7814a(14) =9843a(15) =12196a(16) =14897a(17) =17970a(18) =21439a(19) =25328a(20) =29661a(21) =34462a(22) =39755a(23) =45564a(24) =51913a(25) =58826a(26) =66327a(27) =74440a(28) =83189a(29) =92598