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Number of n X n 0,1 arrays indicating 2X2 subblocks of some larger (n+1)X(n+1) binary array having a sum of two or less, with rows and columns of the latter in lexicographically nondecreasing order
0

%I #5 Dec 18 2015 18:18:37

%S 2,9,98,2201,112349,13855163,4307345460

%N Number of n X n 0,1 arrays indicating 2X2 subblocks of some larger (n+1)X(n+1) binary array having a sum of two or less, with rows and columns of the latter in lexicographically nondecreasing order

%C Diagonal of A227263

%e Some solutions for n=4

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

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

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

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

%K nonn

%O 1,1

%A _R. H. Hardin_ Jul 04 2013