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%I #8 Aug 19 2018 18:13:02
%S 1,1512,624937680,808742880,87348127500,139103775360,150780265560,
%T 261880857000
%N Unitary harmonic numbers m such that the harmonic mean of the unitary divisors of m is also a unitary harmonic number.
%C The harmonic means of the unitary divisors of the terms are 1, 6, 45, 45, 45, 90, 45, 90.
%e 1512 is in the sequence since the harmonic mean of its divisors is 6 and 6 is also a unitary harmonic number.
%t 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}]
%Y Cf. A006086, A317476.
%K nonn,more
%O 1,2
%A _Amiram Eldar_, Jul 29 2018
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