%I #9 Jun 06 2014 17:16:33
%S 1,2,4,8,32,192,1728,25920,518400,14515200,609638400,36578304000,
%T 3292047360000,444426393600000,86663146752000000,24785659971072000000,
%U 10360405867908096000000,6299126767688122368000000
%N Number of n X n symmetric binary matrices with each 1 adjacent to exactly 1 antidiagonally neighboring 1.
%H R. H. Hardin, <a href="/A191650/b191650.txt">Table of n, a(n) for n = 1..51</a>
%e Some solutions for n=5:
%e ..0..0..0..0..0....0..1..0..0..0....0..1..0..0..1....0..1..0..0..0
%e ..0..0..1..0..0....1..0..1..0..0....1..0..1..1..0....1..0..1..0..0
%e ..0..1..0..1..0....0..1..0..1..0....0..1..0..1..0....0..1..0..1..0
%e ..0..0..1..0..0....0..0..1..0..1....0..1..1..0..1....0..0..1..0..0
%e ..0..0..0..0..0....0..0..0..1..0....1..0..0..1..0....0..0..0..0..0
%K nonn
%O 1,2
%A _R. H. Hardin_, Jun 10 2011
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