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A126225 Least number k>0 such that numerator of Sum[ 1/Prime[i]^n, {i,1,k} ] is a prime. 0
2, 2, 3, 2, 3, 5, 3, 11, 3, 22 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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]

LINKS

Table of n, a(n) for n=1..10.

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]

CROSSREFS

Sequence in context: A037126 A080092 A164738 * A306997 A056160 A106245

Adjacent sequences:  A126222 A126223 A126224 * A126226 A126227 A126228

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk, Mar 08 2007

STATUS

approved

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Last modified April 25 21:06 EDT 2019. Contains 322461 sequences. (Running on oeis4.)