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 A069809 #21 Sep 08 2022 08:45:05 %S A069809 1,8,9,18,24,40,56,84,88,104,136,152,156,184,228,232,248,296,328,344, %T A069809 360,372,376,424,444,472,488,516,536,568,584,632,664,712,732,776,792, %U A069809 804,808,824,856,872,876,904,948,1016,1048,1096,1112,1164,1192,1208 %N A069809 Numbers k such that gcd(k, phi(k)) = tau(k). %H A069809 Georg Fischer, <a href="/A069809/b069809.txt">Table of n, a(n) for n = 1..2000</a> (first 1835 terms by Marius A. Burtea) %t A069809 Select[Range[1300], GCD[#, EulerPhi[#]] == DivisorSigma[0, #] &] (* _Jayanta Basu_, Mar 21 2013 *) %o A069809 (PARI) for(n=1,1592,if(gcd(n,eulerphi(n))==numdiv(n),print1(n,","))) %o A069809 (Magma) [n: n in [1..2000] | GCD(n,EulerPhi(n)) eq NumberOfDivisors(n) ];// _Marius A. Burtea_, Dec 28 2018 %Y A069809 Cf. A000005, A000010, A009195. %K A069809 easy,nonn %O A069809 1,2 %A A069809 _Benoit Cloitre_, Apr 30 2002