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A211089 1/4 the number of n X n 0..3 symmetric matrices with every element equal to one or two horizontal and vertical neighbors 0
0, 1, 6, 348, 28140, 8126604, 5661794106, 11445238420311, 62094025253816664, 936614735379619968930, 38691771579576015771775929 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A047941 A229501 A289738 * A221923 A000409 A214445

Adjacent sequences:  A211086 A211087 A211088 * A211090 A211091 A211092

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 31 2012

STATUS

approved

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Last modified August 9 23:26 EDT 2020. Contains 336335 sequences. (Running on oeis4.)