%I #6 Nov 25 2018 13:05:10
%S 1,2,2,6,3,21,12,118,56,959,333,9892,3038,154506,38869,3291314,689349,
%T 103050492,17202265,4328976863,615532072,271539093065,30694296121,
%U 22908330863086,2181826599454,2875160955130336,217661432837240
%N Number of ways of placing non-attacking knights on an n X n chessboard symmetric about the diagonal and under 90-degree rotation.
%K nonn
%O 0,2
%A _R. H. Hardin_, Aug 25 2008