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A210902
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Number of n X n 0..2 symmetric matrices with every element equal to zero, two or three 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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1, 3, 17, 252, 6328, 297609, 25886499, 4205102578, 1265408306700, 707818003940086, 733897633220152333, 1410044723992401143016
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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..0....0..0..0..0....0..1..0..0....0..1..2..2....0..1..2..1
..1..2..0..1....0..1..0..0....1..2..0..0....1..0..2..2....1..0..1..0
..2..0..2..0....0..0..1..0....0..0..1..0....2..2..0..1....2..1..2..1
..0..1..0..1....0..0..0..0....0..0..0..0....2..2..1..2....1..0..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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