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A223443
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4-level binary fanout graph coloring a rectangular array: number of n X 2 0..14 arrays where 0..14 label nodes of a graph with edges 0,1 1,3 3,5 3,6 1,4 4,7 4,8 0,2 2,9 9,11 9,12 2,10 10,13 10,14 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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28, 104, 408, 1616, 6432, 25664, 102528, 409856, 1638912, 6554624, 26216448, 104861696, 419438592, 1677737984, 6710919168, 26843611136, 107374313472, 429496991744, 1717987442688, 6871948722176, 27487792791552, 109951166971904
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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) - 8*a(n-2) for n>3.
G.f.: 4*x*(7 - 16*x + 2*x^2) / ((1 - 2*x)*(1 - 4*x)).
a(n) = 2^(n-2) * (4+25*2^n) for n>1.
(End)
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EXAMPLE
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Some solutions for n=3:
.10.13....1..0....9.11....4..7...10..2...12..9....1..3....1..4....3..5....4..1
.13.10....3..1....2..9....8..4...14.10....9.12....3..6....3..1....6..3....1..0
.10.14....5..3....0..2....4..8...10.13....2..9....1..3....1..3....3..1....4..1
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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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