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A329859
Numbers k such that k and uphi(k) have the same set of prime divisors, where uphi is the unitary totient function (A047994).
1
1, 12, 36, 168, 240, 504, 702, 720, 1176, 1200, 1344, 1404, 1620, 3528, 3600, 4032, 4050, 6480, 8100, 9408, 14880, 19656, 22680, 23250, 28080, 28224, 32400, 44640, 46500, 53460, 63882, 65280, 69750, 74400, 113400, 127764, 132678, 133650, 137592, 139500
OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1052 (terms below 5*10^10)
EXAMPLE
12 is in the sequence since 12 = 2^2 * 3 and uphi(12) = 6 = 2 * 3 both have the same set of prime divisors, {2, 3}.
MATHEMATICA
rad[n_] := Times @@ (First@# & /@ FactorInteger@ n); uphi[1] = 1; uphi[n_] := Times @@ (-1 + Power @@@ FactorInteger[n]); Select[Range[10^5], rad[#] == rad[uphi[#]] &]
CROSSREFS
The unitary version of A055744.
Sequence in context: A238923 A135178 A278583 * A216381 A085331 A225100
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 22 2019
STATUS
approved