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A211081 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, 936, 210780, 181263453, 596226368451, 7500390386674716, 360860802332072507724, 66401649279259441073029473, 46730621582712339208520777565573 (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..2..1..3....2..2..3..3....2..2..3..3....2..0..1..2....2..0..3..2

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

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

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

CROSSREFS

Sequence in context: A173953 A211105 A276637 * A197449 A264640 A211086

Adjacent sequences:  A211078 A211079 A211080 * A211082 A211083 A211084

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 31 2012

STATUS

approved

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Last modified January 19 17:26 EST 2022. Contains 350466 sequences. (Running on oeis4.)