Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric about the diagonal and under 90-degree rotation.
A143891
Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric about the diagonal and under 90-degree rotation.
Terms
- a(0) =1a(1) =2a(2) =1a(3) =5a(4) =2a(5) =15a(6) =7a(7) =68a(8) =23a(9) =370a(10) =104a(11) =2649a(12) =571a(13) =25209a(14) =4176a(15) =313503a(16) =39827a(17) =5212881a(18) =500254a(19) =114569731a(20) =8348616
External references
- oeis: A143891