Number of ways to place 2 nonattacking nightriders on an n X n cylindrical board.

Terms

a(0) =0a(1) =4a(2) =18a(3) =80a(4) =200a(5) =420a(6) =756a(7) =1472a(8) =2358a(9) =3860a(10) =5500a(11) =8304a(12) =11232a(13) =15484a(14) =21090a(15) =27392a(16) =34816a(17) =44604a(18) =55404a(19) =69840a(20) =84294a(21) =102124a(22) =122452a(23) =147264a(24) =173800a(25) =203476a(26) =237762a(27) =276752a(28) =318304a(29) =368340