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A206048
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Number of (n+1) X 3 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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255, 2310, 20400, 180195, 1590378, 14037225, 123893883, 1093502865, 9651382368, 85184227872, 751845910863, 6635879577384, 58569045932253, 516937220242281, 4562548107080751, 40269580936702038, 355424011046747292
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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) = 9*a(n-1) + a(n-2) - 24*a(n-3) + 15*a(n-4) - 6*a(n-5) + 4*a(n-6).
Empirical g.f.: 3*x*(85 + 5*x - 215*x^2 + 135*x^3 - 54*x^4 + 36*x^5) / (1 - 9*x - x^2 + 24*x^3 - 15*x^4 + 6*x^5 - 4*x^6). - Colin Barker, Jun 13 2018
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EXAMPLE
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Some solutions for n=4:
..1..2..1....0..2..0....2..0..0....0..2..2....0..1..2....2..1..2....1..1..1
..2..2..0....0..0..0....0..0..1....2..2..1....0..1..1....0..1..2....0..0..1
..0..0..0....2..0..1....0..1..1....2..0..1....0..1..0....0..1..1....2..0..0
..2..0..1....2..0..0....1..1..2....2..0..1....0..0..0....0..1..2....2..2..2
..2..0..0....2..2..0....2..2..2....2..0..1....1..0..1....0..1..1....1..1..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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