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Number of ways to place two non-attacking queens on all free n-ominoes.
0

%I #3 Nov 11 2014 20:16:20

%S 0,0,0,2,21,131,733,3882,19641,97282

%N Number of ways to place two non-attacking queens on all free n-ominoes.

%e The pentomino XXXX admits 2 combinations of 2 non-attacking queens.

%e ............. X

%K nonn

%O 1,4

%A _David Scambler_, Aug 27 2010