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A210923 Number of n X n 0..3 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order 1
1, 5, 166, 35207, 30211455, 99371076165, 1250065064815292, 60143467055359131310, 11066941546543240934864887, 7788436930452056534815427874703, 20963150916521213172749181596782816735 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

EXAMPLE

Some solutions for n=4

..0..0..2..3....0..1..1..1....0..0..1..3....0..1..0..3....0..1..3..0

..0..1..0..2....1..0..2..3....0..0..1..2....1..2..2..0....1..2..2..0

..2..0..2..3....1..2..1..2....1..1..2..3....0..2..1..3....3..2..0..1

..3..2..3..2....1..3..2..3....3..2..3..0....3..0..3..0....0..0..1..0

CROSSREFS

Sequence in context: A259613 A047940 A229414 * A229524 A288352 A301949

Adjacent sequences:  A210920 A210921 A210922 * A210924 A210925 A210926

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified January 25 17:35 EST 2022. Contains 350572 sequences. (Running on oeis4.)