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%I #5 Mar 31 2012 12:36:19
%S 4,12,52,308,2520,29268,471012,10566004,331575100,14510475976,
%T 885694047808,75478844279780,8975435807171244,1489232331953993836,
%U 344849471434261285096,111434896145450843664604
%N Number of (n+1)X(n+1) symmetric binary matrices without the pattern 1 1 vertically, antidiagonally or horizontally
%H R. H. Hardin, <a href="/A190342/b190342.txt">Table of n, a(n) for n = 1..39</a>
%e Some solutions for 3X3
%e ..0..0..0....0..0..1....1..0..1....1..0..0....0..0..0....1..0..0....0..0..0
%e ..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..1..0....0..1..0
%e ..0..0..0....1..0..0....1..0..0....0..0..1....0..0..1....0..0..1....0..0..0
%K nonn
%O 1,1
%A _R. H. Hardin_ May 09 2011
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