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A126225
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Least number k>0 such that numerator of Sum[ 1/Prime[i]^n, {i,1,k} ] is a prime.
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0
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OFFSET
| 1,1
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COMMENTS
| a(12) > 80, a(13) = 30, a(14) = 16, a(18) = 7, a(19) = 3. [From J. Mulder (jasper.mulder(AT)planet.nl), Jan 25 2010]
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MATHEMATICA
| a[n_] := Block[{i = 1, sum = 0}, While[True, sum += 1/Prime[i]^n; If[PrimeQ[Numerator@sum], Return[i]]; i++ ]] [From J. Mulder (jasper.mulder(AT)planet.nl), Jan 25 2010]
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CROSSREFS
| Sequence in context: A037126 A080092 A164738 * A056160 A106245 A129568
Adjacent sequences: A126222 A126223 A126224 * A126226 A126227 A126228
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KEYWORD
| hard,more,nonn
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AUTHOR
| Alexander Adamchuk (alex(AT)kolmogorov.com), Mar 08 2007
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