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A183344
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Number of n X 2 binary arrays with each 1 adjacent to exactly one 0 vertically and one 0 horizontally.
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1
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1, 7, 9, 17, 33, 59, 109, 201, 369, 679, 1249, 2297, 4225, 7771, 14293, 26289, 48353, 88935, 163577, 300865, 553377, 1017819, 1872061, 3443257, 6333137, 11648455, 21424849, 39406441, 72479745, 133311035, 245197221, 450988001, 829496257
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OFFSET
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1,2
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COMMENTS
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Column 2 of A183352.
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..200
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FORMULA
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Empirical: a(n) = a(n-1) + a(n-2) + a(n-3).
Empirical g.f.: x*(1 + 6*x + x^2) / (1 - x - x^2 - x^3). - Colin Barker, Mar 27 2018
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EXAMPLE
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Some solutions for 5 X 2:
..0..1....0..0....0..0....0..0....0..1....0..0....0..0....1..0....0..0....1..0
..0..0....0..0....0..0....1..0....0..0....1..0....1..0....0..0....0..0....0..0
..1..0....0..0....1..0....1..0....0..1....1..0....1..0....0..1....0..0....1..0
..1..0....0..0....1..0....0..0....0..1....0..0....0..0....0..1....0..0....1..0
..0..1....0..1....0..1....0..0....0..0....0..1....1..0....1..0....1..0....0..0
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CROSSREFS
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Cf. A183352.
Sequence in context: A140364 A022321 A194830 * A255830 A256613 A116484
Adjacent sequences: A183341 A183342 A183343 * A183345 A183346 A183347
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Jan 04 2011
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STATUS
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approved
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