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A210898
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Number of n X n 0..2 symmetric matrices with every element equal to zero 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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1, 3, 17, 199, 3494, 98664, 4322895, 299203520, 32406437104, 5516394350943, 1472647280151852, 617087491407309762, 405686597596735406852
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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=3
..0..1..0....0..1..0....0..1..2....0..0..1....0..1..2....0..1..2....0..1..2
..1..0..1....1..2..1....1..2..1....0..0..2....1..2..0....1..0..0....1..2..1
..0..1..2....0..1..2....2..1..0....1..2..1....2..0..1....2..0..0....2..1..2
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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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