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A210904
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Number of n X n 0..2 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order
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1
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1, 5, 108, 7722, 1640736, 1033777404, 1931855614272, 10707730229352132, 176032647122454516348, 8583448868806218541129800, 1241375815868250678950006865216, 532497522393110319522129344363284548
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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..1....0..1..1..0....0..1..1..0....0..1..1..2
..1..0..1..0....0..1..2..0....1..0..1..0....1..1..0..2....1..2..1..0
..2..1..2..2....0..2..1..0....1..1..2..1....1..0..0..1....1..1..1..0
..0..0..2..2....1..0..0..2....0..0..1..0....0..2..1..1....2..0..0..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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