This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A068581 #16 Jun 12 2022 02:58:46 %S A068581 1,17,23,29,31,37,43,51,55,65,69,77,82,87,91,93,94,95,106,111,118,122, %T A068581 128,129,133,134,136,142,146,158,165,170,184,195,218,230,231,232,238, %U A068581 243,246,248,250,254,273,282,285,286,290,296,297,310,318,322,344,351 %N A068581 Let phi_m(x) = phi(phi(...(phi(x))...)) m times; sequence gives values of k such that phi_4(k) = tau(k). %C A068581 Last term is a(132) = 7560. %C A068581 Numbers k such that A049100(k) = A000005(k). %H A068581 Jinyuan Wang, <a href="/A068581/b068581.txt">Table of n, a(n) for n = 1..132</a> %t A068581 Select[Range[351], Nest[EulerPhi, #, 4] === DivisorSigma[0, #] &] (* _Amiram Eldar_, Jun 12 2022 *) %Y A068581 Cf. A000005, A000010, A049100, A068579, A068580, A068582. %K A068581 nonn,easy,fini,full %O A068581 1,2 %A A068581 _Benoit Cloitre_, Mar 26 2002