A193276 Composite numbers n such that phi(n) divides 3n - 3.

9, 21, 65, 1729, 3201, 4125441

Offset

1,1

Comments

Next term > 10^9.

Links

Table of n, a(n) for n=1..6.

Mathematica

t={}; Do[If[PrimeQ[n]==False&&IntegerQ[(n-1)*3/EulerPhi[n]], Print[n]; AppendTo[t, n]], {n, 2, 10^5}]; t
Select[Range[413*10^4], CompositeQ[#]&&Mod[3#-3, EulerPhi[#]]==0&] (* Harvey P. Dale, Nov 02 2024 *)

Prog

(PARI) p=3; forprime(q=5, 1e8, forstep(n=p\4*4, q-1, 4, if((3*n-3)%eulerphi(n)==0, print1(n", "))); p=q) \\ Charles R Greathouse IV, Jul 24 2011

Crossrefs

Sequence in context: A338007 A147466 A262055 * A173084 A137340 A075640

Adjacent sequences: A193273 A193274 A193275 * A193277 A193278 A193279

Keyword

nonn

Author

José María Grau Ribas, Jul 20 2011

Status

approved