OFFSET
1,2
COMMENTS
The harmonic means of the unitary divisors of the terms are 1, 6, 45, 45, 45, 90, 45, 90.
EXAMPLE
1512 is in the sequence since the harmonic mean of its divisors is 6 and 6 is also a unitary harmonic number.
MATHEMATICA
usigma[n_] := If[n == 1, 1, Times @@ (1 + Power @@@ FactorInteger[n])]; ud[n_] := 2^PrimeNu[n]; uhQ[n_] := IntegerQ[n*ud[n]/usigma[n]]; uhuhQ[n_] := Module[{m = n*ud[n]/usigma[n]}, IntegerQ[m] && uhQ[m]]; Do[If[uhuhQ[n], Print[n]], {n, 1, 10^11}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Jul 29 2018
STATUS
approved