A192335 Numbers n such that phi(n) divides rad(n).

1, 2, 4, 6, 18

Offset

1,2

Comments

Terms are all of the form n = 2^a * 3^b with a <= 2 (else 4 | rad(n)) and b <= 2 (else 9 | rad(n)), hence the sequence is finite. [Charles R Greathouse IV, Jun 29 2011]

Links

Table of n, a(n) for n=1..5.

Mathematica

Rad[n_] := Times @@ Transpose[FactorInteger[n]][[1]]; Select[Range[10^6], Mod[Rad[#], EulerPhi[#]] == 0 &]

Prog

(PARI) rad(n)=n=factor(n)[, 1]; prod(i=1, #n, n[i])
for(n=1, 2^2*3^2, if(rad(n)%eulerphi(n)==0, print1(n", "))) \\ Charles R Greathouse IV, Jun 29 2011

Crossrefs

Cf. A000010, A007947.

Sequence in context: A367127 A294920 A046441 * A334390 A067993 A074131

Adjacent sequences: A192332 A192333 A192334 * A192336 A192337 A192338

Keyword

nonn,fini,full

Author

José María Grau Ribas, Jun 28 2011

Status

approved