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A210901 Number of n X n 0..2 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order 0
1, 2, 20, 464, 22564, 2472584, 603871080, 327862785884, 395850912855384, 1063574508841830552, 6358546221961060404292, 84578736940287879637237736 (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..2..1....0..1..2..1....0..1..2..2....0..1..0..1....0..1..0..2

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

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

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

CROSSREFS

Sequence in context: A009160 A188811 A009252 * A274572 A292396 A274738

Adjacent sequences:  A210898 A210899 A210900 * A210902 A210903 A210904

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified January 28 01:01 EST 2022. Contains 350654 sequences. (Running on oeis4.)