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 A071387 #24 Mar 28 2024 09:03:38
%S A071387 0,2,8,32,40,48,396,704,72,216,144,1056,360,384,1320,240,9000,7128,
%T A071387 480,1296,15936,3072,864,7344,720,4992,2016,6000,4752,3024,9984,1920,
%U A071387 7560,22848,29160,3360,13248,27720,9072,9360,4032,4800,16896,3840,9504,23520,5040
%N A071387 Smallest number k for which the set of solutions to phi(x) = k has 2n-1 entries.
%H A071387 Amiram Eldar, <a href="/A071387/b071387.txt">Table of n, a(n) for n = 1..1000</a>
%H A071387 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (see invphi.gp there).
%F A071387 a(n) = Min({x; Card(InvPhi(x)) = 2n-1}); a(1)=0 because of Carmichael conjecture.
%e A071387 For n = 7: 2n-1 = 13, a(7) = Min(InvPhi(13)) = Min({396,400,420,552,560,660}) = 396.
%o A071387 (PARI) a(n) = {if (n==1, return (0)); my(k=1); while(#invphi(k) != 2*n-1, k++); k;} \\ _Michel Marcus_, May 13 2020
%Y A071387 Cf. A000010 (phi), A014197, A058277, A063512, A071386, A071388, A071389.
%K A071387 nonn
%O A071387 1,2
%A A071387 _Labos Elemer_, May 23 2002
%E A071387 a(12)-a(47) from _Donovan Johnson_, Jul 27 2011