a(n) = 121*n^2 - 204*n + 86.

Terms

a(0) =3a(1) =162a(2) =563a(3) =1206a(4) =2091a(5) =3218a(6) =4587a(7) =6198a(8) =8051a(9) =10146a(10) =12483a(11) =15062a(12) =17883a(13) =20946a(14) =24251a(15) =27798a(16) =31587a(17) =35618a(18) =39891a(19) =44406a(20) =49163a(21) =54162a(22) =59403a(23) =64886a(24) =70611a(25) =76578a(26) =82787a(27) =89238a(28) =95931a(29) =102866