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 A227381 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 one, with rows and columns of the latter in lexicographically nondecreasing order 1
 2, 7, 54, 1104, 61127, 8988949, 3657501287 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Diagonal of A227385 LINKS EXAMPLE Some solutions for n=4 ..0..0..1..0....0..0..0..0....0..1..0..0....0..0..1..0....0..0..1..0 ..1..0..0..1....0..1..0..0....1..0..0..1....0..1..0..1....1..0..0..0 ..0..0..1..0....1..0..0..0....0..1..1..0....0..0..1..1....0..0..0..1 ..0..0..0..1....0..0..0..0....0..0..0..0....0..0..1..1....0..1..1..0 CROSSREFS Sequence in context: A283335 A326207 A280221 * A182055 A211209 A271440 Adjacent sequences:  A227378 A227379 A227380 * A227382 A227383 A227384 KEYWORD nonn AUTHOR R. H. Hardin Jul 09 2013 STATUS approved

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Last modified May 16 15:55 EDT 2021. Contains 343949 sequences. (Running on oeis4.)