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A211084 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors 0
1, 10, 228, 13227, 1888962, 662705112, 570731832303, 1205311139476404, 6235576486183465116, 78976030794422736761688 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A052789 A092254 A211079 * A302095 A276019 A004702

Adjacent sequences:  A211081 A211082 A211083 * A211085 A211086 A211087

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 31 2012

STATUS

approved

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Last modified October 28 21:20 EDT 2020. Contains 338064 sequences. (Running on oeis4.)