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Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation.
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%I #3 Mar 31 2012 12:35:09

%S 1,1,1,5,29,139,901,5485,74291,1056181,24810777,651071773,25748617719,

%T 1169149922235,81072042123257,6590052771959131

%N Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation.

%e Maximal 8 X 8 example

%e .1.1.0.1.0.1.1.1

%e .1.1.0.1.1.0.1.1

%e .1.0.0.1.1.0.0.0

%e .0.1.1.0.0.1.1.1

%e .1.1.1.0.0.1.1.0

%e .0.0.0.1.1.0.0.1

%e .1.1.0.1.1.0.1.1

%e .1.1.1.0.1.0.1.1

%K nonn

%O 1,4

%A _R. H. Hardin_, Oct 26 2008