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%I #8 Mar 15 2023 11:18:30
%S 1,1,3,10,42,244,2031,22714,342292,6943430,188479666,6843502049,
%T 331910774405,21483424837024,1854744805774187,213498320443922663,
%U 32758157589935274374
%N Half the number of n X n symmetric binary matrices with no element unequal to a strict majority of its diagonal, vertical and horizontal neighbors.
%e Some solutions for n=5 with a(1,1)=0:
%e ..0..0..1..1..1....0..0..0..0..0....0..0..0..0..0....0..0..0..0..0
%e ..0..0..0..1..1....0..1..1..1..0....0..0..0..1..1....0..1..1..0..0
%e ..1..0..0..0..0....0..1..1..1..1....0..0..1..1..1....0..1..1..1..1
%e ..1..1..0..0..0....0..1..1..1..1....0..1..1..1..1....0..0..1..1..1
%e ..1..1..0..0..0....0..0..1..1..1....0..1..1..1..1....0..0..1..1..1
%K nonn
%O 1,3
%A _R. H. Hardin_, May 16 2011
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