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, 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

Author

Amiram Eldar, Nov 22 2019

Keywords

• nonn

Examples

			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}.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..1052 (terms below 5*10^10)

Crossrefs

The unitary version of A055744.

Cf. A007947, A027598, A047994.

Programs

Mathematica

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