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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

Table of n, a(n) for n=1..7.

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.)