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A210927
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Number of n X n 0..3 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order
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1
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OFFSET
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1,2
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LINKS
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EXAMPLE
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Some solutions for n=4
..0..0..1..1....0..1..2..1....0..0..2..1....0..0..1..0....0..1..1..0
..0..0..2..2....1..1..2..1....0..1..3..3....0..1..2..2....1..0..0..1
..1..2..3..1....2..2..0..3....2..3..2..0....1..2..2..0....1..0..0..1
..1..2..1..0....1..1..3..3....1..3..0..0....0..2..0..2....0..1..1..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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