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A210929 Number of n X n 0..3 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order 0
1, 3, 42, 2316, 320744, 106842320, 85415568160, 163885278844480, 754594332585922688, 8337847863812427968768, 221082535444417970063262208 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A333323 A331705 A156108 * A083402 A145984 A213956

Adjacent sequences:  A210926 A210927 A210928 * A210930 A210931 A210932

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified September 18 09:05 EDT 2021. Contains 347518 sequences. (Running on oeis4.)