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Number of n X n symmetric binary arrays with rows, considered as binary numbers, in nondecreasing order, and all main diagonal and antidiagonal elements zero
1

%I #5 Dec 18 2015 18:17:21

%S 1,1,2,3,10,23,161,643,10399,76674,2793020,39088170,3075920130,

%T 83293952237,13726688369636,728989553713898,246651220048842038,

%U 25910326192430212792,17788328684183351444219,3714881265827493365084899

%N Number of n X n symmetric binary arrays with rows, considered as binary numbers, in nondecreasing order, and all main diagonal and antidiagonal elements zero

%H R. H. Hardin, <a href="/A162034/b162034.txt">Table of n, a(n) for n=1..23</a>

%K nonn

%O 1,3

%A _R. H. Hardin_ Jun 25 2009