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A223212
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3X3X3 triangular graph coloring a rectangular array: number of nX2 0..5 arrays where 0..5 label nodes of a graph with edges 0,1 0,2 1,2 1,3 1,4 2,4 3,4 2,5 4,5 and every array movement to a horizontal or vertical neighbor moves along an edge of this graph
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1
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18, 126, 918, 6642, 48114, 348462, 2523798, 18278946, 132387858, 958837662, 6944516694, 50296639122, 364280484978, 2638352661966, 19108640336598, 138397015977282, 1002359858893074, 7259732297153982, 52579632512961558
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 6*a(n-1) +9*a(n-2).
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EXAMPLE
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Some solutions for n=3
..0..1....1..4....0..1....0..2....4..1....4..1....4..2....2..4....0..2....5..2
..2..4....2..1....1..0....1..4....1..2....2..4....2..4....4..1....2..0....2..5
..0..2....1..2....4..1....3..1....4..1....4..2....0..2....1..2....0..1....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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