A317477 Unitary harmonic numbers m such that the harmonic mean of the unitary divisors of m is also a unitary harmonic number.

1, 1512, 624937680, 808742880, 87348127500, 139103775360, 150780265560, 261880857000

Offset: 1

Author

Amiram Eldar, Jul 29 2018

Keywords

• nonn
• more

Comments

The harmonic means of the unitary divisors of the terms are 1, 6, 45, 45, 45, 90, 45, 90.

Examples

			1512 is in the sequence since the harmonic mean of its divisors is 6 and 6 is also a unitary harmonic number.
		

Crossrefs

Cf. A006086, A317476.

Programs

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}]