A094469 - OEIS

%I #17 Mar 07 2020 06:51:54

%S 1,2,3,6,1645,3290,4935,9870,3831674,11495022,346014339,692028678

%N Numbers k such that sum of 11th powers of divisors of k is divisible by the square of Euler-phi of k.

%F A013959(k)/A000010(k)^2 is integer.

%t Do[ If[ Mod[ DivisorSigma[11, n], EulerPhi[n]^2] == 0, Print[n]], {n, 10^7}] (* _Robert G. Wilson v_, May 23 2004 *)

%o (PARI) isok(k) = (sigma(k, 11) % eulerphi(k)^2) == 0; \\ _Michel Marcus_, Mar 07 2020

%Y Cf. A000010, A013959, A015763, A091285.

%K nonn,more

%O 1,2

%A _Labos Elemer_, May 19 2004

%E a(9) from _Robert G. Wilson v_, May 23 2004

%E a(10) from _Labos Elemer_, May 26 2004

%E a(6) corrected and a(11)-a(12) added by _Amiram Eldar_, Mar 07 2020