Number of ways to place 7 nonattacking knights on a 7 X n board.

Terms

a(0) =1a(1) =78a(2) =1758a(3) =38588a(4) =383246a(5) =2135344a(6) =8891854a(7) =30108310a(8) =86669806a(9) =219845764a(10) =504261973a(11) =1065642840a(12) =2104251027a(13) =3924818982a(14) =6973786593a(15) =11884673662a(16) =19532410762a(17) =31097451768a(18) =48140491605a(19) =72688612756a(20) =107333684073