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A211091 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors 0
1, 9, 324, 36801, 13804290, 17121995676, 70150653652257, 949536762106019733, 42462806002512959389608, 6273638029264294190600689986 (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..2..3....1..2..0..0....0..3..2..2....1..3..3..0....1..0..3..2

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

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

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

CROSSREFS

Sequence in context: A128788 A164080 A211087 * A124070 A203763 A041619

Adjacent sequences:  A211088 A211089 A211090 * A211092 A211093 A211094

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 31 2012

STATUS

approved

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Last modified September 25 08:41 EDT 2020. Contains 337335 sequences. (Running on oeis4.)