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A211090 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors 1
1, 16, 993, 236025, 215258400, 752872084911, 10098360926130825, 519450490659204066717, 102470951001660755232267828, 77521214457887124644680695382314 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..11

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A187802 A181199 A024301 * A160012 A070307 A159683

Adjacent sequences:  A211087 A211088 A211089 * A211091 A211092 A211093

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 31 2012

STATUS

approved

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Last modified September 23 13:34 EDT 2020. Contains 337310 sequences. (Running on oeis4.)