%I #4 Dec 18 2015 18:17:23
%S 2,4,8,21,53,145,405,1180,3562,11030,35306,115338,387443,1326992,
%T 4650201,16604351,60443887,223971602,844095896,3234044019,12582749734,
%U 49703821584,199149007691,809153896365,3331563584486
%N Number of n X n symmetric binary arrays with rows, considered as graycode numbers, in strictly increasing order, and no more than 2 ones in any row or column
%K nonn
%O 1,1
%A _R. H. Hardin_ Jun 25 2009