Number of ways to place 2 non-attacking ferses on an n X n board.

Terms

a(0) =0a(1) =4a(2) =28a(3) =102a(4) =268a(5) =580a(6) =1104a(7) =1918a(8) =3112a(9) =4788a(10) =7060a(11) =10054a(12) =13908a(13) =18772a(14) =24808a(15) =32190a(16) =41104a(17) =51748a(18) =64332a(19) =79078a(20) =96220a(21) =116004a(22) =138688a(23) =164542a(24) =193848a(25) =226900a(26) =264004a(27) =305478a(28) =351652a(29) =402868