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%I #5 Mar 25 2022 18:47:34
%S 1,1,1,3,13,35,181,1303,13131,161693,2592581,57377381,1720164275,
%T 69927099465,3715147371129,261988046119405,24980387570081613,
%U 3210146525819915095,550205755804555982181,125514016677735094761717
%N Number of n X n binary arrays symmetric about main diagonal with all 1's connected only in a 2 X 2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation.
%e Maximal 8 X 8 example
%e .0.0.0.0.0.0.1.1
%e .0.0.0.0.0.0.1.1
%e .0.0.0.1.1.1.0.1
%e .0.0.1.0.1.1.0.0
%e .0.0.1.1.0.0.1.1
%e .0.0.1.1.0.0.1.1
%e .1.1.0.0.1.1.0.1
%e .1.1.1.0.1.1.1.0
%K nonn
%O 1,4
%A _R. H. Hardin_, Oct 26 2008
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