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A183323 Number of n X n binary arrays with each 1 adjacent to exactly two other 1s 0
1, 2, 6, 27, 289, 4740, 128371, 6115158, 505971397, 73890230419, 19136191954838, 8704355999401819, 6908686513461201175, 9552034660752931158279 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Diagonal of A183328

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

Some solutions for 6X6

..1..1..1..0..0..0....0..1..1..1..1..0....0..0..0..1..1..1....0..0..1..1..1..1

..1..0..1..0..1..1....0..1..0..0..1..1....0..0..1..1..0..1....0..0..1..0..0..1

..1..0..1..0..1..1....1..1..0..0..0..1....0..1..1..0..1..1....1..1..1..0..0..1

..1..1..1..0..0..0....1..0..0..0..1..1....0..1..0..1..1..0....1..0..0..0..0..1

..0..0..0..1..1..0....1..1..0..1..1..0....0..1..0..1..0..0....1..0..0..0..1..1

..0..0..0..1..1..0....0..1..1..1..0..0....0..1..1..1..0..0....1..1..1..1..1..0

CROSSREFS

Sequence in context: A003513 A113731 A113676 * A153253 A174880 A303394

Adjacent sequences:  A183320 A183321 A183322 * A183324 A183325 A183326

KEYWORD

nonn

AUTHOR

R. H. Hardin Jan 03 2011

STATUS

approved

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Last modified August 19 10:38 EDT 2022. Contains 356228 sequences. (Running on oeis4.)