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 A015126 #24 Nov 14 2024 05:53:25
%S A015126 1,1,3,3,5,3,7,5,7,5,11,5,13,7,15,15,17,7,19,15,13,11,23,15,25,13,19,
%T A015126 13,29,15,31,17,25,17,35,13,37,19,35,17,41,13,43,25,35,23,47,17,43,25,
%U A015126 51,35,53,19,41,35,37,29,59,17,61,31,37,51,65,25,67,51,69,35,71,35,73
%N A015126 Least k such that phi(k) = phi(n).
%C A015126 From _Jianing Song_, Nov 11 2022: (Start)
%C A015126 The first even term is a(33817088) = 16842752 (see A002181 and A143510).
%C A015126 Conjecture: a(n) is always odd for odd n. (End)
%H A015126 Antti Karttunen, <a href="/A015126/b015126.txt">Table of n, a(n) for n = 1..10000</a>
%H A015126 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%o A015126 (PARI) a(n) = {my(en = eulerphi(n)); k = 1; while (eulerphi(k) != en, k++); return (k);} \\ _Michel Marcus_, Jun 17 2013
%o A015126 (PARI) a(n) = vecmin(select(x -> x<=n, invphi(eulerphi(n)))); \\ _Amiram Eldar_, Nov 14 2024, using _Max Alekseyev_'s invphi.gp
%Y A015126 Cf. A000010, A028476, A066412, A066659.
%Y A015126 Cf. A002181, A143510.
%K A015126 nonn,look
%O A015126 1,3
%A A015126 _Vladeta Jovovic_, Jan 12 2002