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A210902 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, 17, 252, 6328, 297609, 25886499, 4205102578, 1265408306700, 707818003940086, 733897633220152333, 1410044723992401143016 (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..0....0..0..0..0....0..1..0..0....0..1..2..2....0..1..2..1

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

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

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

CROSSREFS

Sequence in context: A331649 A322737 A201107 * A188803 A084040 A009495

Adjacent sequences:  A210899 A210900 A210901 * A210903 A210904 A210905

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified January 29 05:09 EST 2022. Contains 350672 sequences. (Running on oeis4.)