A329858 Numbers k such that k and usigma(k) have the same set of prime divisors, where usigma(k) is the sum of unitary divisors of k (A034448).

1, 6, 24, 60, 90, 180, 360, 378, 816, 1056, 1512, 3780, 9100, 10500, 12240, 13230, 15750, 15840, 26460, 31500, 36750, 40950, 46494, 51408, 52920, 63000, 63700, 66528, 73500, 87360, 94500, 95550, 110250, 145600, 145920, 147000, 163800, 181632, 185976, 220500

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..435 (terms below 5*10^10)

Example

6 is in the sequence since 6 = 2 * 3 and usigma(6) = 12 = 2^2 * 3 both have the same set of prime divisors, {2, 3}.

Mathematica

rad[n_] := Times @@ (First@# & /@ FactorInteger@ n); usigma[1]=1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); Select[Range[2*10^5], rad[#] == rad[usigma[#]] &]

Crossrefs

The unitary version of A027598.

Cf. A007947, A034448.

Sequence in context: A212904 A264790 A201598 * A211615 A195647 A086768

Adjacent sequences: A329855 A329856 A329857 * A329859 A329860 A329861

Keyword

nonn

Author

Amiram Eldar, Nov 22 2019

Status

approved