a(n) = (9*n + 4)^2.

Terms

a(0) =16a(1) =169a(2) =484a(3) =961a(4) =1600a(5) =2401a(6) =3364a(7) =4489a(8) =5776a(9) =7225a(10) =8836a(11) =10609a(12) =12544a(13) =14641a(14) =16900a(15) =19321a(16) =21904a(17) =24649a(18) =27556a(19) =30625a(20) =33856a(21) =37249a(22) =40804a(23) =44521a(24) =48400a(25) =52441a(26) =56644a(27) =61009a(28) =65536a(29) =70225