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A208722
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Number of 2n-bead necklaces labeled with numbers 1..n not allowing reversal, with neighbors differing by exactly 1.
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2
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0, 1, 4, 15, 52, 210, 796, 3175, 12468, 49288, 194140, 766110, 3019224, 11905330, 46938192, 185111095, 730148332, 2880799554, 11369141308, 44881708072, 177229210656, 700047776214, 2765947680124, 10931565973950, 43215517211240, 170888480306500
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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LINKS
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Andrew Howroyd, Table of n, a(n) for n = 1..100
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EXAMPLE
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All solutions for n=4:
..1....1....3....2....1....2....2....2....2....1....1....1....1....1....1
..2....2....4....3....2....3....3....3....3....2....2....2....2....2....2
..1....3....3....2....3....2....4....4....2....3....1....1....3....3....1
..2....4....4....3....2....3....3....3....3....2....2....2....4....2....2
..3....3....3....2....1....2....4....2....4....3....1....3....3....3....1
..2....4....4....3....2....3....3....3....3....4....2....4....2....2....2
..3....3....3....2....3....4....4....4....4....3....1....3....3....3....3
..2....2....4....3....2....3....3....3....3....2....2....2....2....2....2
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CROSSREFS
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Diagonal of A208727.
Sequence in context: A329253 A161125 A027295 * A057332 A230623 A162978
Adjacent sequences: A208719 A208720 A208721 * A208723 A208724 A208725
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Mar 01 2012
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EXTENSIONS
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a(13)-a(26) from Andrew Howroyd, Mar 18 2017
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STATUS
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approved
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