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%I #6 Dec 18 2015 18:17:39
%S 1,1,3,7,21,122,880,6953,72647,1129137,24364420,694152879,24831611879,
%T 1208655194306,80157177796753,7105061448777651
%N Number of n X n symmetric binary matrices with each 1 adjacent to exactly 1 knight-move neighboring 1
%e Some solutions for n=4
%e ..0..0..0..0....0..1..0..0....0..0..0..0....0..0..1..0....0..0..0..0
%e ..0..0..0..0....1..0..0..1....0..0..1..1....0..0..0..0....0..0..0..1
%e ..0..0..0..0....0..0..0..0....0..1..0..0....1..0..0..1....0..0..0..1
%e ..0..0..0..0....0..1..0..0....0..1..0..0....0..0..1..0....0..1..1..0
%K nonn
%O 1,3
%A _R. H. Hardin_ May 29 2011
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