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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

Table of n, a(n) for n=1..11.

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: A092480 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 October 16 01:52 EDT 2021. Contains 348034 sequences. (Running on oeis4.)