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A210907
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Number of n X n 0..2 symmetric matrices with every element equal to one or two horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order
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0
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0, 1, 2, 51, 1726, 153098, 28152650, 11567939904, 10468180657260, 20883980738963652, 92033224229940826385, 894504588855167462245204
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OFFSET
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1,3
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LINKS
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EXAMPLE
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Some solutions for n=4
..0..0..1..1....0..0..0..0....0..0..0..0....0..0..2..2....0..0..1..2
..0..0..2..0....0..1..1..0....0..1..1..0....0..1..1..2....0..0..1..2
..1..2..2..0....0..1..1..0....0..1..2..2....2..1..1..1....1..1..1..0
..1..0..0..0....0..0..0..0....0..0..2..2....2..2..1..1....2..2..0..0
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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