The OEIS is supported by the many generous donors to the OEIS Foundation.
Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #13 Jun 12 2022 02:58:41
%S 1,41,47,53,59,61,67,71,73,79,85,109,115,119,123,125,127,141,143,145,
%T 155,159,161,163,166,177,178,183,185,194,201,202,203,206,209,213,214,
%U 215,217,219,226,237,247,255,259,262,278,298,301,302,314,327,328,343
%N Let phi_m(x) = phi(phi(...(phi(x))...)) m times; sequence gives values of k such that phi_5(k) = tau(k).
%C Last term is a(340) = 24570.
%C Numbers k such that A049107(k) = A000005(k).
%H Jinyuan Wang, <a href="/A068582/b068582.txt">Table of n, a(n) for n = 1..340</a>
%t Select[Range[343], Nest[EulerPhi, #, 5] === DivisorSigma[0, #] &] (* _Amiram Eldar_, Jun 12 2022 *)
%Y Cf. A000005, A000010, A049107, A068579, A068580, A068581.
%K nonn,easy,fini,full
%O 1,2
%A _Benoit Cloitre_, Mar 26 2002