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Number of n X n binary matrices with floor(n^2/2) 1's and rows and columns in lexicographically nondecreasing order
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%I #3 Dec 18 2015 18:17:26

%S 1,3,10,121,3680,326650,91271990,74872992399,208579984612008,

%T 1748923742658486631

%N Number of n X n binary matrices with floor(n^2/2) 1's and rows and columns in lexicographically nondecreasing order

%C Diagonal of A180979

%e All solutions for 3X3

%e ..0..0..0....0..0..0....0..0..0....0..0..1....0..0..1....0..0..1....0..0..1

%e ..0..1..1....0..0..1....0..1..1....0..1..0....0..0..1....0..1..0....0..1..0

%e ..0..1..1....1..1..1....1..0..1....0..1..1....0..1..1....1..1..0....1..0..1

%e ...

%e ..0..0..1....0..0..1....0..1..1

%e ..0..0..1....0..1..1....1..0..0

%e ..1..1..0....1..0..0....1..0..0

%K nonn

%O 1,2

%A _R. H. Hardin_ Sep 30 2010