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A209067
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Number of n-bead necklaces labeled with numbers -2..2 not allowing reversal, with sum zero and avoiding the pattern z z+1 z+2.
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0
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1, 3, 6, 22, 70, 265, 1007, 4055, 16593, 69429, 294509, 1265692, 5494398, 24065829, 106207739, 471840078, 2108406146, 9470071142, 42731427358, 193612759011, 880517540867
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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Some solutions for n=6:
.-2...-2...-2...-2...-2...-2...-1...-2...-2...-2...-2...-2...-2...-2...-2...-1
..1...-1....2....1...-1....1...-1...-1....2....0....1....1....0...-2...-1...-1
..2....1....0....0...-1....0....1...-2...-1...-1....1...-1....0...-2....2....0
..0....1...-1....1....2....2...-1....1....2....1....0....1....1....2...-1....0
..0...-1....2...-2....1....0....0....2....0....0...-2....1....1....2....0....0
.-1....2...-1....2....1...-1....2....2...-1....2....2....0....0....2....2....2
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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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