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A210900
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Number of n X n 0..2 symmetric matrices with every element equal to zero, one or two 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, 102, 6390, 1086041, 502575673, 633196217205, 2172041686544831, 20286478141700961127, 515885869356108286483984, 35719903989356689494965133243, 6734055759629373955660905711394302
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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..0..1....0..1..2..2....0..0..1..1....0..1..1..2....0..0..1..1
..1..0..1..1....1..1..0..1....0..1..2..0....1..1..0..0....0..1..0..0
..0..1..1..2....2..0..2..0....1..2..1..2....1..0..1..0....1..0..2..2
..1..1..2..2....2..1..0..1....1..0..2..2....2..0..0..1....1..0..2..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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