A143891 - OEIS

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.

%I #7 Nov 25 2018 12:29:53

%S 1,2,1,5,2,15,7,68,23,370,104,2649,571,25209,4176,313503,39827,

%T 5212881,500254,114569731,8348616

%N 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.

%K nonn,more,hard

%O 0,2

%A _R. H. Hardin_, Sep 04 2008