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 A136683 Numbers k such that A136675(k) is prime. 8
 2, 3, 4, 5, 6, 9, 20, 21, 29, 119, 132, 151, 351, 434, 457, 462, 572, 611, 930, 1107, 1157, 1452, 1515, 2838, 3997, 5346, 6463, 6725, 7664, 10234, 14168, 14299 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A136675(k) = Numerator of Sum_{j=1..k} (-1)^(j+1)/j^3. LINKS Table of n, a(n) for n=1..32. Eric Weisstein's World of Mathematics, Harmonic Number MATHEMATICA Do[ f=Numerator[ Sum[ (-1)^(k+1)*1/k^3, {k, 1, n} ] ]; If[ PrimeQ[f], Print[ {n, f} ] ], {n, 1, 151} ] Flatten[Position[Numerator[Accumulate[Table[(-1)^(k+1) 1/k^3, {k, 3000}]]], _?PrimeQ] ] (* Harvey P. Dale, Feb 12 2013 *) PROG (PARI) isok(n) = ispseudoprime(numerator(sum(k=1, n, (-1)^(k+1) / k^3))); \\ Daniel Suteu, Mar 15 2019 CROSSREFS Cf. A058313, A119682, A120296, A136675, A136676, A136677. Cf. A001008, A007406, A007408, A007410, A099828, A103345. Cf. A136681, A136682, A136684, A136685, A136686. Sequence in context: A211676 A076299 A341015 * A200332 A303953 A195185 Adjacent sequences: A136680 A136681 A136682 * A136684 A136685 A136686 KEYWORD nonn,more AUTHOR Alexander Adamchuk, Jan 16 2008 EXTENSIONS More terms from Harvey P. Dale, Feb 12 2013 a(25)-a(28) from Amiram Eldar, Mar 15 2019 a(29)-a(32) from Robert Price, Apr 22 2019 STATUS approved

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Last modified July 25 03:09 EDT 2024. Contains 374586 sequences. (Running on oeis4.)