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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Diagonal of A227263

LINKS

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

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 A357825 A187647

Adjacent sequences: A227255 A227256 A227257 * A227259 A227260 A227261

KEYWORD

nonn

AUTHOR

R. H. Hardin Jul 04 2013

STATUS

approved

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Last modified February 6 11:11 EST 2023. Contains 360104 sequences. (Running on oeis4.)