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

Terms

a(0) =0a(1) =4a(2) =18a(3) =92a(4) =230a(5) =522a(6) =1022a(7) =1808a(8) =2970a(9) =4610a(10) =6842a(11) =9792a(12) =13598a(13) =18410a(14) =24390a(15) =31712a(16) =40562a(17) =51138a(18) =63650a(19) =78320a(20) =95382a(21) =115082a(22) =137678a(23) =163440a(24) =192650a(25) =225602a(26) =262602a(27) =303968a(28) =350030a(29) =401130