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A210904 Number of n X n 0..2 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order 1
1, 5, 108, 7722, 1640736, 1033777404, 1931855614272, 10707730229352132, 176032647122454516348, 8583448868806218541129800, 1241375815868250678950006865216, 532497522393110319522129344363284548 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..16

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A204110 A113056 A220549 * A048564 A139971 A305095

Adjacent sequences:  A210901 A210902 A210903 * A210905 A210906 A210907

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified June 21 21:26 EDT 2018. Contains 305644 sequences. (Running on oeis4.)