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A211037
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, 34, 398, 6988, 197328, 8645790, 598407040, 64812874208, 11032788701886, 2945294560303704, 1234174982814619524, 811373195193470813704
OFFSET
1,2
EXAMPLE
Some solutions for n=4
..1..1..1..0....2..1..1..1....1..0..2..0....2..1..0..1....1..1..0..2
..1..0..1..2....1..1..2..1....0..2..0..2....1..0..1..0....1..1..2..1
..1..1..1..0....1..2..0..1....2..0..2..0....0..1..2..1....0..2..1..2
..0..2..0..1....1..1..1..1....0..2..0..1....1..0..1..0....2..1..2..1
CROSSREFS
Sequence in context: A362771 A276753 A226554 * A130607 A211042 A086345
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 30 2012
STATUS
approved