a(n) = (6*n + 4)^2.

Terms

a(0) =16a(1) =100a(2) =256a(3) =484a(4) =784a(5) =1156a(6) =1600a(7) =2116a(8) =2704a(9) =3364a(10) =4096a(11) =4900a(12) =5776a(13) =6724a(14) =7744a(15) =8836a(16) =10000a(17) =11236a(18) =12544a(19) =13924a(20) =15376a(21) =16900a(22) =18496a(23) =20164a(24) =21904a(25) =23716a(26) =25600a(27) =27556a(28) =29584a(29) =31684