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A208104
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Number of n X 4 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 1 1 and 1 1 0 vertically.
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1
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9, 81, 169, 361, 841, 2025, 5041, 12769, 32761, 84681, 219961, 573049, 1495729, 3908529, 10220809, 26739241, 69973225, 183142089, 479391025, 1254930625, 3285238489, 8600522121, 22515902809, 58946498521, 154322479921, 404019140625
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OFFSET
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1,1
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COMMENTS
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Column 4 of A208108.
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..210
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FORMULA
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Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 6*a(n-3) + 4*a(n-4) + 2*a(n-5) - a(n-6) for n>7.
Empirical g.f.: x*(9 + 45*x - 137*x^2 - 99*x^3 + 185*x^4 + 55*x^5 - 40*x^6) / ((1 - x)*(1 + x)*(1 - 3*x + x^2)*(1 - x - x^2)). - Colin Barker, Jun 28 2018
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EXAMPLE
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Some solutions for n=10:
..1..1..0..1....1..1..0..1....0..1..1..1....0..1..1..0....0..0..1..1
..0..1..1..1....1..1..0..0....0..1..1..0....0..1..1..1....1..1..1..0
..1..1..0..1....1..1..0..1....0..1..1..1....1..1..1..0....0..0..1..1
..0..1..1..1....1..1..0..0....0..1..1..0....0..1..1..0....0..1..1..0
..1..1..0..1....1..1..1..1....1..1..1..1....1..1..1..1....1..0..1..1
..0..1..1..1....1..1..0..0....0..1..1..0....0..1..1..0....0..1..1..0
..1..1..0..1....1..1..1..1....1..1..1..1....1..1..1..1....1..0..1..1
..0..1..1..1....1..1..0..0....0..1..1..0....0..1..1..0....0..1..1..0
..1..1..0..1....1..1..0..1....1..1..1..0....0..1..1..1....1..0..1..1
..0..1..1..1....1..1..0..0....0..1..1..0....1..1..1..0....0..1..1..0
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CROSSREFS
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Cf. A208108.
Sequence in context: A207678 A207684 A207510 * A207725 A044260 A208109
Adjacent sequences: A208101 A208102 A208103 * A208105 A208106 A208107
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Feb 23 2012
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STATUS
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approved
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