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A210910 Number of n X n 0..2 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order 0
1, 3, 23, 401, 13984, 970083, 132838634, 35924634547, 19142194392682, 20077037322761989, 41429745313369193161, 168164789977096418548306 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

Some solutions for n=4

..0..1..0..0....0..1..0..1....0..1..2..2....0..1..0..0....0..1..0..1

..1..0..0..0....1..2..2..0....1..2..2..2....1..2..0..0....1..2..2..2

..0..0..1..0....0..2..2..1....2..2..0..1....0..0..2..0....0..2..2..2

..0..0..0..0....1..0..1..0....2..2..1..2....0..0..0..0....1..2..2..0

CROSSREFS

Sequence in context: A233218 A114601 A178315 * A280654 A118195 A055326

Adjacent sequences:  A210907 A210908 A210909 * A210911 A210912 A210913

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified August 9 14:27 EDT 2020. Contains 336323 sequences. (Running on oeis4.)