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 A066705 #11 Nov 14 2024 05:54:05
%S A066705 0,1,0,3,0,4,0,5,7,8,0,10,0,9,0,15,0,14,0,16,13,11,0,20,0,21,19,26,0,
%T A066705 24,0,17,25,32,0,28,0,27,35,34,0,36,0,33,39,23,0,40,43,44,0,45,0,38,
%U A066705 41,52,37,29,0,48,0,31,57,51,0,50,0,64,0,56,0,70,0,63,55,74,61,72,0,68,0
%N A066705 Greatest k < n such that phi(k) = phi(n) if such k exists, otherwise 0.
%H A066705 Amiram Eldar, <a href="/A066705/b066705.txt">Table of n, a(n) for n = 1..10000</a>
%H A066705 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%o A066705 (PARI) a(n) = {my(v = select(x -> x<n, invphi(eulerphi(n)))); if(#v == 0, 0, vecmax(v));} \\ _Amiram Eldar_, Nov 14 2024, using _Max Alekseyev_'s invphi.gp
%Y A066705 Cf. A000010, A015126, A028476, A043343, A066659.
%K A066705 nonn
%O A066705 1,4
%A A066705 _Vladeta Jovovic_, Jan 14 2002