a(n) = (8n + 3)^2.

Terms

a(0) =9a(1) =121a(2) =361a(3) =729a(4) =1225a(5) =1849a(6) =2601a(7) =3481a(8) =4489a(9) =5625a(10) =6889a(11) =8281a(12) =9801a(13) =11449a(14) =13225a(15) =15129a(16) =17161a(17) =19321a(18) =21609a(19) =24025a(20) =26569a(21) =29241a(22) =32041a(23) =34969a(24) =38025a(25) =41209a(26) =44521a(27) =47961a(28) =51529a(29) =55225