OFFSET
1,2
COMMENTS
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.
EXAMPLE
270 is in the sequence since the harmonic mean of its divisors is 6, which is also a harmonic number.
MATHEMATICA
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}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Jul 29 2018
STATUS
approved