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A208667
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Number of 2n-bead necklaces labelled with numbers 1..4 allowing reversal, with neighbors differing by exactly 1
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0
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3, 5, 8, 14, 24, 47, 89, 187, 396, 881, 1990, 4645, 10935, 26211, 63320, 154378, 378444, 933023, 2308957, 5735372, 14286908, 35683815, 89324138, 224057919
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OFFSET
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1,1
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COMMENTS
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Column 4 of A208671
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LINKS
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Table of n, a(n) for n=1..24.
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EXAMPLE
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All solutions for n=4
..1....2....2....2....1....1....1....1....1....3....1....1....2....2
..2....3....3....3....2....2....2....2....2....4....2....2....3....3
..1....2....2....2....1....1....3....3....3....3....3....1....4....4
..2....3....3....3....2....2....4....2....2....4....2....2....3....3
..1....4....2....2....3....1....3....1....3....3....3....3....2....4
..2....3....3....3....4....2....4....2....4....4....2....2....3....3
..1....4....2....4....3....3....3....3....3....3....3....3....4....4
..2....3....3....3....2....2....2....2....2....4....2....2....3....3
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CROSSREFS
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Sequence in context: A109022 A023596 A086661 * A078065 A175378 A072655
Adjacent sequences: A208664 A208665 A208666 * A208668 A208669 A208670
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin Feb 29 2012
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STATUS
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approved
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