Number of ways to place 2 nonattacking kings on an n X n cylindrical chessboard.

Terms

a(0) =0a(1) =0a(2) =9a(3) =68a(4) =215a(5) =504a(6) =1001a(7) =1784a(8) =2943a(9) =4580a(10) =6809a(11) =9756a(12) =13559a(13) =18368a(14) =24345a(15) =31664a(16) =40511a(17) =51084a(18) =63593a(19) =78260a(20) =95319a(21) =115016a(22) =137609a(23) =163368a(24) =192575a(25) =225524a(26) =262521a(27) =303884a(28) =349943a(29) =401040