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A211046 1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors 0
1, 5, 40, 516, 10632, 351016, 18493208, 1556661888, 208981813872, 44758689895632, 15281461874812576, 8316915639373762736, 7212900527703818038976 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A088695 A145166 A113079 * A138427 A277405 A280572

Adjacent sequences:  A211043 A211044 A211045 * A211047 A211048 A211049

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 30 2012

STATUS

approved

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Last modified September 30 01:05 EDT 2022. Contains 357092 sequences. (Running on oeis4.)