Number of ways to place 4 nonattacking amazons (superqueens) on a 4 X n board.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =12a(8) =60a(9) =180a(10) =432a(11) =900a(12) =1692a(13) =2940a(14) =4800a(15) =7452a(16) =11100a(17) =15972a(18) =22320a(19) =30420a(20) =40572a(21) =53100a(22) =68352a(23) =86700a(24) =108540a(25) =134292a(26) =164400a(27) =199332a(28) =239580a(29) =285660