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Number of n X n binary arrays symmetric about both diagonal and antidiagonal 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 1,1,1,1,1,3,9,19,37,115,481,2395,10969,57003,371055,2992969,26653005,

%T 266091447,3019768963,42043911685,666291390951,12240477419651,

%U 251570549673017,6156133419360705,172490682719945137

%N Number of n X n binary arrays symmetric about both diagonal and antidiagonal 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 .0.0.0.0.1.1.0.0

%e .0.0.0.0.1.1.0.0

%e .0.0.0.0.1.0.1.1

%e .0.0.0.0.0.1.1.1

%e .1.1.1.0.0.0.0.0

%e .1.1.0.1.0.0.0.0

%e .0.0.1.1.0.0.0.0

%e .0.0.1.1.0.0.0.0

%K nonn

%O 1,6

%A _R. H. Hardin_, Oct 26 2008