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A209108
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Number of n-bead necklaces labeled with numbers -1..1 not allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.
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1
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1, 2, 1, 5, 5, 15, 25, 68, 139, 354, 813, 2047, 4935, 12421, 30833, 78102, 197139, 503132, 1284711, 3302155, 8503965, 21996761, 57026957, 148322398, 386626825, 1010375144, 2645762431, 6942725217, 18251279163, 48065184969, 126783827201
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OFFSET
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1,2
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COMMENTS
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Column 1 of A209115.
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..32
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EXAMPLE
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All solutions for n=6:
.-1...-1...-1...-1...-1...-1...-1...-1...-1...-1....0...-1...-1...-1...-1
.-1...-1...-1....0....0....1....0....1...-1....1....0...-1....0...-1....0
..1....1....1....0....0...-1...-1....0...-1...-1....0....1....0....0....0
..1....1....0....1....0....1....1....0....1....1....0...-1....1....0...-1
..0...-1....0....0....0...-1....0....0....1....0....0....1...-1....1....1
..0....1....1....0....1....1....1....0....1....0....0....1....1....1....1
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CROSSREFS
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Sequence in context: A086905 A167638 A317878 * A269019 A184234 A193816
Adjacent sequences: A209105 A209106 A209107 * A209109 A209110 A209111
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Mar 05 2012
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STATUS
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approved
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