Odd squares: a(n) = (2n+1)^2. Also centered octagonal numbers.

Terms

a(0) =1a(1) =9a(2) =25a(3) =49a(4) =81a(5) =121a(6) =169a(7) =225a(8) =289a(9) =361a(10) =441a(11) =529a(12) =625a(13) =729a(14) =841a(15) =961a(16) =1089a(17) =1225a(18) =1369a(19) =1521a(20) =1681a(21) =1849a(22) =2025a(23) =2209a(24) =2401a(25) =2601a(26) =2809a(27) =3025a(28) =3249a(29) =3481