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A211087 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors 1
1, 9, 324, 35343, 12487068, 14118092100, 51199696832895, 595365272306224965, 22199455509688700548632, 2654252181204304007637930258, 1017614219466672806577892453493568 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..12

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A156634 A128788 A164080 * A211091 A124070 A203763

Adjacent sequences:  A211084 A211085 A211086 * A211088 A211089 A211090

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 31 2012

STATUS

approved

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Last modified September 24 14:00 EDT 2020. Contains 337321 sequences. (Running on oeis4.)