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A227258
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
2, 9, 98, 2201, 112349, 13855163, 4307345460
OFFSET
1,1
COMMENTS
Diagonal of A227263
EXAMPLE
Some solutions for n=4
..1..1..1..0....1..1..1..1....1..1..1..1....1..1..1..0....1..1..0..0
..1..0..0..1....1..0..1..1....1..0..1..1....1..0..0..0....1..1..1..0
..0..1..1..1....1..1..0..1....1..1..1..0....1..0..0..1....1..1..1..1
..0..0..1..1....1..1..0..0....0..1..0..0....0..0..0..1....0..1..1..1
CROSSREFS
Sequence in context: A317275 A013057 A237929 * A027686 A360696 A357825
KEYWORD
nonn
AUTHOR
R. H. Hardin Jul 04 2013
STATUS
approved