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A211077 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, 297, 30213, 9904329, 10357083063, 34636341072699, 370225462363917579, 12650055630492583306593, 1381655999590131944779825905, 482381759955085135355798493794163 (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

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

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

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

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

CROSSREFS

Sequence in context: A003303 A012838 A216966 * A211082 A061685 A183549

Adjacent sequences:  A211074 A211075 A211076 * A211078 A211079 A211080

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 31 2012

STATUS

approved

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Last modified February 29 09:41 EST 2020. Contains 332355 sequences. (Running on oeis4.)