Number of ways to place 7 nonattacking amazons (superqueens) on a 7 X n board.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =2a(9) =100a(10) =908a(11) =4872a(12) =19818a(13) =66864a(14) =193926a(15) =498924a(16) =1165544a(17) =2517036a(18) =5089430a(19) =9731908a(20) =17735888a(21) =30999920a(22) =52234274a(23) =85210284a(24) =135059570a(25) =208627984a(26) =314889330a(27) =465423908a(28) =674966914a(29) =962031720