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A211042 1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors 0
1, 5, 34, 504, 12656, 595218, 51772998, 8410205156, 2530816613400, 1415636007880172, 1467795266440304666, 2820089447984802286032 (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

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

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

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

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

CROSSREFS

Sequence in context: A226554 A211037 A130607 * A086345 A295545 A309534

Adjacent sequences:  A211039 A211040 A211041 * A211043 A211044 A211045

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 30 2012

STATUS

approved

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Last modified October 4 18:23 EDT 2022. Contains 357239 sequences. (Running on oeis4.)