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Numbers k such that phi(k) | sigma_3(k).
11

%I #12 Jun 23 2019 13:15:18

%S 1,2,3,6,12,14,15,30,35,38,42,54,56,70,78,87,95,105,114,126,135,140,

%T 147,168,174,182,190,209,210,215,216,222,248,258,264,270,285,294,297,

%U 315,357,418,420,430,455,456,540,546,551,570,594,609,616,627

%N Numbers k such that phi(k) | sigma_3(k).

%C sigma_3(k) is the sum of the cubes of the divisors of k (A001158).

%H Amiram Eldar, <a href="/A015761/b015761.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[630], Divisible[DivisorSigma[3, #], EulerPhi[#]] &] (* _Amiram Eldar_, Jun 23 2019 *)

%o (PARI) isok(k) = (sigma(k, 3) % eulerphi(k)) == 0; \\ _Michel Marcus_, Jun 23 2019

%Y Cf. A000010, A001158.

%K nonn

%O 1,2

%A _Robert G. Wilson v_