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A211086
1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors
1
1, 16, 960, 229824, 219386880, 834532651008, 12650446296013824, 764188858823853957120, 183961835921396390619045888, 176476517080094726836047543951360
OFFSET
1,2
LINKS
EXAMPLE
Some solutions for n=4
..0..2..0..2....0..0..2..3....0..0..0..3....0..2..1..2....0..2..3..0
..2..1..1..0....0..1..2..1....0..2..0..3....2..0..0..2....2..2..3..2
..0..1..2..3....2..2..0..3....0..0..2..2....1..0..1..3....3..3..1..3
..2..0..3..0....3..1..3..0....3..3..2..0....2..2..3..0....0..2..3..2
CROSSREFS
Sequence in context: A211081 A197449 A264640 * A187802 A181199 A024301
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 31 2012
STATUS
approved