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A210905 Number of n X n 0..2 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order 0
1, 2, 24, 552, 27204, 2812168, 611509240, 279902590168, 269562004096692, 546187771866465456, 2328406266027562097220, 20883572160878878738558896, 394075725737300936910238275696 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A054946 A046744 A000186 * A012113 A156525 A170904

Adjacent sequences:  A210902 A210903 A210904 * A210906 A210907 A210908

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified April 17 21:53 EDT 2021. Contains 343071 sequences. (Running on oeis4.)