a(n) = (8*n + 5)^2.

Terms

a(0) =25a(1) =169a(2) =441a(3) =841a(4) =1369a(5) =2025a(6) =2809a(7) =3721a(8) =4761a(9) =5929a(10) =7225a(11) =8649a(12) =10201a(13) =11881a(14) =13689a(15) =15625a(16) =17689a(17) =19881a(18) =22201a(19) =24649a(20) =27225a(21) =29929a(22) =32761a(23) =35721a(24) =38809a(25) =42025a(26) =45369a(27) =48841a(28) =52441a(29) =56169