a(n) = 8*n^2 + 8*n + 4.

Terms

a(0) =4a(1) =20a(2) =52a(3) =100a(4) =164a(5) =244a(6) =340a(7) =452a(8) =580a(9) =724a(10) =884a(11) =1060a(12) =1252a(13) =1460a(14) =1684a(15) =1924a(16) =2180a(17) =2452a(18) =2740a(19) =3044a(20) =3364a(21) =3700a(22) =4052a(23) =4420a(24) =4804a(25) =5204a(26) =5620a(27) =6052a(28) =6500a(29) =6964