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A208998
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Number of 7-bead necklaces labeled with numbers -n..n not allowing reversal, with sum zero and first differences in -n..n.
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1
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9, 155, 1111, 4935, 16307, 44209, 104001, 219929, 428031, 779487, 1344353, 2215747, 3514415, 5393753, 8045199, 11704103, 16655941, 23243017, 31871521, 43019059, 57242537, 75186543, 97592047, 125305621, 159288983, 200629037, 250548251
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) + a(n-2) + a(n-3) - a(n-4) - 2*a(n-5) - a(n-6) + a(n-8) + a(n-9) + a(n-10) + a(n-12) - a(n-13) - a(n-15) - a(n-16) - a(n-17) + a(n-19) + 2*a(n-20) + a(n-21) - a(n-22) - a(n-23) - a(n-24) + a(n-25).
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EXAMPLE
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Some solutions for n=6:
-5 -5 -2 -6 -6 -3 -4 -2 -2 -5 -4 -3 -5 -6 -4 -4
0 0 -1 -1 0 -2 1 1 2 1 -1 -1 -1 -3 -4 -2
3 3 1 2 3 4 -2 0 1 0 -2 0 1 2 1 0
0 4 1 3 5 -2 1 0 -1 -2 2 3 -1 2 -1 4
1 0 -2 6 3 1 3 0 0 1 0 1 2 1 4 3
3 1 2 0 -1 1 0 2 0 5 5 1 4 5 3 -3
-2 -3 1 -4 -4 1 1 -1 0 0 0 -1 0 -1 1 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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