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A250209
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a(n) = least k such that k * n is in A072226, or 0 if no such k exists.
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1
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2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 5, 1, 2, 2, 1, 2, 1, 6, 1, 1, 2, 5, 1, 1, 1, 1, 1, 8, 34, 8, 1, 2, 1, 10, 1, 2, 350, 2, 1, 111, 4, 1, 3, 16, 4, 15, 28, 3, 1, 206, 3, 10, 2, 1, 1, 2, 3, 1, 15, 637, 12, 1, 4, 22, 17, 104, 4, 2, 1012, 1, 1
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OFFSET
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1,1
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COMMENTS
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Conjecture: a(n) > 0 for all n.
Numbers n such that n * a(n) > 10^5, a(n) is currently unknown for n = 121, 124, 130, 143, 144, 162, 164, 171, 172, 185, 188, 197, 201, 215, ...
a(121) = (A117545(2048))/11 and they are both currently unknown.
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LINKS
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MATHEMATICA
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Table[k=1; while[!PrimeQ[Cyclotomic[n*k, 2]], k++]; k, {n, 150}]
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PROG
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(PARI) a(n) = {k = 1; while (!isprime(polcyclo(k*n, 2)), k++); k; } \\ Michel Marcus, Jan 18 2015
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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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