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Search: id:A109628
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| A109628 |
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Numbers n such that the numerator of sum_{k=1..n} 1/prime{k), in reduced form, is prime. |
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+0
3
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| 2, 3, 5, 6, 18, 19, 22, 47, 57, 58, 63, 70, 73, 112, 632, 1382
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Terms <= 112 correspond to certified primes.
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EXAMPLE
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sum_{k=1..6} 1/prime(k) = 40361/30030, and 40361 is prime, hence 6 is a term.
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MATHEMATICA
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s = 0; Do[s += 1/Prime[n]; k = Numerator[s]; If[PrimeQ[k], Print[n]], {n, 1, 1500}]
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CROSSREFS
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Sequence in context: A079226 A055686 A126250 this_sequence A102977 A131599 A076384
Adjacent sequences: A109625 A109626 A109627 this_sequence A109629 A109630 A109631
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KEYWORD
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hard,more,nonn
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AUTHOR
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Ryan Propper (rpropper(AT)stanford.edu), Aug 02 2005
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