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A205919
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Number of (n+1) X 2 0..3 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to one, and every 2 X 2 determinant nonzero.
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1
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76, 389, 1828, 9144, 43572, 215294, 1035724, 5082472, 24576282, 120140890, 582580746, 2841986300, 13802576730, 67255368928, 326915006288, 1591943059154, 7741739157470, 37686051760598, 183317203390912, 892200827543090
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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) = a(n-1) + 18*a(n-2) + 3*a(n-3) - 2*a(n-4) + 26*a(n-5) + 28*a(n-6) + 8*a(n-7).
Empirical g.f.: x*(76 + 313*x + 71*x^2 + 86*x^3 + 509*x^4 + 448*x^5 + 116*x^6) / (1 - x - 18*x^2 - 3*x^3 + 2*x^4 - 26*x^5 - 28*x^6 - 8*x^7). - Colin Barker, Jun 13 2018
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EXAMPLE
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Some solutions for n=4:
..3..2....2..1....3..1....0..1....3..0....3..1....0..1....0..3....1..1....3..1
..3..0....2..2....1..1....1..1....3..3....1..1....1..1....1..1....3..0....3..3
..3..3....1..2....0..1....0..1....3..1....0..1....2..1....1..2....3..3....3..0
..2..3....2..2....1..1....1..1....1..1....1..1....1..1....1..1....2..3....3..3
..2..2....3..0....0..1....2..0....3..0....3..0....2..0....0..1....2..2....1..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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