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7, 47, 42131, 23763863, 192066102203, 5733412167187, 34745876421709, 185813891783454008069, 171312804637561107990389, 29207630124216024960052176833, 6300447575454970515437116064749
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history;
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..11.
Eric Weisstein's World of Mathematics, Harmonic Number.
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EXAMPLE
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A124837(n) begins {1, 7, 47, 57, 459, 341, 3349, 3601, 42131, 44441, ...}.
Thus a(1) = 7, a(2) = 47, a(3) = 42131.
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MATHEMATICA
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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}]
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CROSSREFS
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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
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KEYWORD
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nonn
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AUTHOR
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Alexander Adamchuk, Nov 11 2006
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EXTENSIONS
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Crossrefs edited by Michel Marcus, Jul 14 2018
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STATUS
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approved
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