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A317476
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Harmonic numbers k such that the harmonic mean of the divisors of k is also a harmonic number.
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1
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OFFSET
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1,2
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COMMENTS
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The harmonic means of the divisors of the terms are 1, 6, 140, 270, 270, 672, 672, 496.
The terms 1, 2701389600 and 71271827200 have harmonic means of divisors which are also in this sequence.
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LINKS
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EXAMPLE
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270 is in the sequence since the harmonic mean of its divisors is 6, which is also a harmonic number.
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MATHEMATICA
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hQ[n_] := IntegerQ[n*DivisorSigma[0, n]/DivisorSigma[1, n]]; hhQ[n_] := Module[{h = n * DivisorSigma[0, n]/DivisorSigma[1, n]}, IntegerQ[h] && hQ[h]]; Do[If[hhQ[n], Print[n]], {n, 1, 10^14}]
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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