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 A124880 Primes in A124837. 3
 7, 47, 42131, 23763863, 192066102203, 5733412167187, 34745876421709, 185813891783454008069, 171312804637561107990389, 29207630124216024960052176833, 6300447575454970515437116064749 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Eric Weisstein's World of Mathematics, Harmonic Number. EXAMPLE A124837(n) begins {1, 7, 47, 57, 459, 341, 3349, 3601, 42131, 44441, ...}. Thus a(1) = 7, a(2) = 47, a(3) = 42131. MATHEMATICA s=3/2; Do[s=s+1/n; f=Numerator[n*(n-1)/2*(s-3/2)]; If[PrimeQ[f], Print[{n-2, f}]], {n, 3, 125}] CROSSREFS A124837 are the numerators of third-order harmonic numbers H(n, (3)). Corresponding numbers n such that A124837(n) is prime are listed in A124881. Cf. A001008, A002805, A067657, A056903, A027612, A124878, A124879, A124837, A124881. Sequence in context: A354211 A292067 A088143 * A227100 A240334 A171312 Adjacent sequences: A124877 A124878 A124879 * A124881 A124882 A124883 KEYWORD nonn AUTHOR Alexander Adamchuk, Nov 11 2006 EXTENSIONS Crossrefs edited by Michel Marcus, Jul 14 2018 STATUS approved

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Last modified March 28 20:24 EDT 2023. Contains 361596 sequences. (Running on oeis4.)