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A211091
1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one, three or four 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
EXTENSIONS
Name corrected by Andrew Howroyd, Mar 25 2025
STATUS
approved

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Last modified April 12 20:33 EDT 2026. Contains 394621 sequences.
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