a(n) = (12*n + 9)^2.

Terms

a(0) =81a(1) =441a(2) =1089a(3) =2025a(4) =3249a(5) =4761a(6) =6561a(7) =8649a(8) =11025a(9) =13689a(10) =16641a(11) =19881a(12) =23409a(13) =27225a(14) =31329a(15) =35721a(16) =40401a(17) =45369a(18) =50625a(19) =56169a(20) =62001a(21) =68121a(22) =74529a(23) =81225a(24) =88209a(25) =95481a(26) =103041a(27) =110889a(28) =119025a(29) =127449