A194855 Numbers n such that phi(n) divides Sum_{k=1..n} phi(k).

1, 2, 3, 4, 6, 7, 10, 15, 16, 17, 18, 20, 22, 25, 35, 36, 37, 38, 54, 92, 140, 162, 212, 303, 320, 455, 456, 974, 1028, 1136, 1296, 1297, 1353, 1869, 2215, 2405, 2548, 3065, 3265, 4230, 4410, 5584, 7886, 21420, 23727, 36001, 60662, 85722, 100117, 117094, 173973

Offset: 1

Author

Carl Najafi, Sep 04 2011

Keywords

• nonn

Links

• Donovan Johnson, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A000010, A002088.

Programs

Mathematica

limit = 200000; sums = Accumulate[EulerPhi[Range[limit]]]; Select[Range[limit], Mod[sums[[#]], EulerPhi[#]] == 0 &] (* Carl Najafi, Sep 05 2011 *)

PARI

isok(n)=sum(k=1,n,eulerphi(k))%eulerphi(n)==0 \\ Anders Hellström, Aug 22 2015

Extensions

More terms from D. S. McNeil, Sep 04 2011