Number of ways to place 4 nonattacking kings on an n X n board.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =79a(5) =1987a(6) =16834a(7) =85275a(8) =317471a(9) =962089a(10) =2515262a(11) =5882109a(12) =12605095a(13) =25175191a(14) =47443474a(15) =85152487a(16) =146608359a(17) =243516365a(18) =392004286a(19) =613859609a(20) =938008287a(21) =1402264459a(22) =2055382210a(23) =2959442131a(24) =4192607119