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

%I #6 Apr 29 2016 20:09:08

%S 0,0,1,7,46,240,1207,6004,28903,137996

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

%e E.g. the triomino XXX admits 1 combination of 2 non-attacking kings.

%K nonn

%O 1,4

%A _David Scambler_, Aug 27 2010