Number of ways to place 4 nonattacking nightriders on a 4 X n board.

Terms

a(0) =1a(1) =16a(2) =84a(3) =412a(4) =1126a(5) =2760a(6) =5739a(7) =10982a(8) =19695a(9) =33068a(10) =52801a(11) =80638a(12) =118731a(13) =169368a(14) =235135a(15) =318890a(16) =423733a(17) =553028a(18) =710389a(19) =899690a(20) =1125059a(21) =1390880a(22) =1701793a(23) =2062694a(24) =2478735a(25) =2955324a(26) =3498125a(27) =4113058a(28) =4806299a(29) =5584280