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A191600 Number of n X n symmetric binary matrices with each 1 adjacent to no more than 1 horizontally, vertically or diagonally neighboring 1 1
2, 5, 23, 159, 1646, 28059, 724310, 29626607, 1890041732, 188477431884, 29421793928187, 7179932235630885, 2740816166752070599, 1636347059803667113339, 1527949588062203773106011 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..20

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A242227 A032182 A165902 * A343020 A167142 A136731

Adjacent sequences:  A191597 A191598 A191599 * A191601 A191602 A191603

KEYWORD

nonn

AUTHOR

R. H. Hardin Jun 08 2011

STATUS

approved

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Last modified June 18 11:58 EDT 2021. Contains 345098 sequences. (Running on oeis4.)