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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).
3
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.
Sequence in context: A212904 A264790 A201598 * A211615 A195647 A086768
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 22 2019
STATUS
approved