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A210925
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Number of n X n 0..3 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order
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0
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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..1..2..3....0..1..2..3....0..1..0..1....0..1..0..3....0..1..2..1
..1..0..1..2....1..0..1..0....1..2..1..3....1..0..2..1....1..2..3..0
..2..1..3..3....2..1..0..2....0..1..2..1....0..2..1..3....2..3..2..3
..3..2..3..3....3..0..2..1....1..3..1..2....3..1..3..0....1..0..3..1
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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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