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 A063470 #18 Nov 16 2024 03:09:16 %S A063470 34,45,52,102,140,156,252,360,420 %N A063470 Numbers n such that tau(n)*4 = phi(n). %C A063470 Phi(n) = k*tau(n) has at most finitely many solutions for any constant k or even for slowly increasing functions like k(n) = n^(epsilon). - _Labos Elemer_, Jul 20 2001 %C A063470 For n > 2, tau(n) > 2 and phi(n) <= n-1 so the least solution a(1) to tau(n)*k = phi(n), must be a(1) >= 2*k+1, for the case k=4, a(1) >= 2*4+1 = 9. - _Enrique Pérez Herrero_, May 12 2012 %F A063470 a(1) = A175667(4) %F A063470 a(A112954(4)) = A112955(4). - _Enrique Pérez Herrero_, May 12 2012 %o A063470 (PARI) for(n=1,10^6, if(numdiv(n)*4==eulerphi(n),print(n))) %Y A063470 Cf. A062516. %Y A063470 Cf. A112954, A020488, A063469. %K A063470 fini,nonn,full %O A063470 1,1 %A A063470 _Jason Earls_, Jul 26 2001 %E A063470 "full" keyword from _Max Alekseyev_, Mar 01 2010