

A317477


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


1




OFFSET

1,2


COMMENTS

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


LINKS

Table of n, a(n) for n=1..8.


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

Cf. A006086, A317476.
Sequence in context: A187294 A107523 A282253 * A064584 A318713 A252508
Adjacent sequences: A317474 A317475 A317476 * A317478 A317479 A317480


KEYWORD

nonn,more


AUTHOR

Amiram Eldar, Jul 29 2018


STATUS

approved



