a(n) = (3*n)^2.

Terms

a(0) =0a(1) =9a(2) =36a(3) =81a(4) =144a(5) =225a(6) =324a(7) =441a(8) =576a(9) =729a(10) =900a(11) =1089a(12) =1296a(13) =1521a(14) =1764a(15) =2025a(16) =2304a(17) =2601a(18) =2916a(19) =3249a(20) =3600a(21) =3969a(22) =4356a(23) =4761a(24) =5184a(25) =5625a(26) =6084a(27) =6561a(28) =7056a(29) =7569