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A206478
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(Number of permutations of {1,2,...,n} for which sums of four consecutive numbers (with wraparound) are all distinct)/2n
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0
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OFFSET
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5,1
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COMMENTS
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Essentially different ways that 1,2,...,n can be placed around a circle so that the sums of three consecutive terms are all distinct.
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LINKS
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EXAMPLE
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a(6)=8 because up to rotation/reflection the only three permutations which work are 123465, 123546, 124653, 125364, 126543, 132456, 132645, 136524.
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CROSSREFS
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KEYWORD
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hard,nonn
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AUTHOR
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STATUS
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approved
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