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A183586
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1/24 the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock containing exactly three distinct values.
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1
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6, 56, 520, 4832, 44896, 417152, 3875968, 36013568, 334620160, 3109124096, 28888434688, 268416966656, 2493996949504, 23172979195904, 215311796961280, 2000570126041088, 18588302571864064, 172713262087405568
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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) = 8*a(n-1) + 12*a(n-2).
G.f.: 2*x*(3 + 4*x) / (1 - 8*x - 12*x^2).
a(n) = ((4-2*sqrt(7))^n*(-5+2* sqrt(7)) + (2*(2+sqrt(7)))^n*(5+2*sqrt(7))) / (6*sqrt(7)).
(End)
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EXAMPLE
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Some solutions with a(1,1)=0 for 3 X 2:
..0..3....0..1....0..3....0..2....0..1....0..3....0..1....0..2....0..2....0..2
..3..1....2..2....1..0....0..1....1..3....2..3....3..3....3..0....1..1....3..2
..0..3....0..1....0..3....0..3....2..2....2..1....0..2....2..2....2..0....3..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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