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A206047
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Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to one.
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1
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48, 255, 1338, 7041, 37020, 194691, 1023822, 5384085, 28313712, 148895799, 783011010, 4117687209, 21654034308, 113873925675, 598838568438, 3149163684861, 16560776867160, 87089576125791, 457985415203562
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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) = 4*a(n-1) +7*a(n-2) -2*a(n-3).
Empirical g.f.: 3*x*(16 + 21*x - 6*x^2) / (1 - 4*x - 7*x^2 + 2*x^3). - Colin Barker, Jun 13 2018
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EXAMPLE
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Some solutions for n=4:
..0..1....0..0....2..1....2..1....1..1....0..1....0..1....0..2....1..2....2..1
..0..0....2..2....2..1....0..0....2..1....0..1....0..0....1..2....1..1....2..2
..1..2....1..2....0..0....1..2....1..1....0..0....2..0....2..2....0..0....1..2
..1..1....1..1....2..0....2..2....1..2....0..1....0..0....0..2....0..1....1..2
..2..1....2..2....0..0....1..1....1..1....1..1....2..2....1..1....0..1....2..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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