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A259517
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Number of (n+1) X (1+1) 0..1 arrays with each 2 X 2 subblock having clockwise pattern 0000 0001 0011 0101 or 1111.
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1
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12, 38, 120, 380, 1204, 3816, 12096, 38344, 121552, 385328, 1221520, 3872320, 12275584, 38914656, 123362816, 391070784, 1239728192, 3930045568, 12458584320, 39494789760, 125201899264, 396900848896, 1258210017536, 3988634573824
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 2*a(n-3).
Empirical g.f.: 2*x*(2 + x)*(3 - 4*x) / (1 - 4*x + 2*x^2 + 2*x^3). - Colin Barker, Dec 25 2018
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EXAMPLE
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Some solutions for n=4:
..0..0....1..1....0..0....0..0....1..0....0..0....0..0....0..0....0..0....0..0
..0..1....1..1....0..1....0..1....0..1....0..0....0..1....1..1....0..1....1..0
..1..0....0..0....1..0....0..0....0..1....0..1....0..0....1..1....1..0....1..0
..0..1....0..1....0..0....0..0....0..0....0..1....1..0....0..0....1..0....0..0
..0..0....0..1....0..0....0..1....1..1....0..0....0..1....1..1....0..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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