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 A066659 #20 Nov 14 2024 05:56:31
%S A066659 2,0,4,6,8,0,9,10,14,12,22,0,21,18,16,20,32,0,27,24,26,0,46,30,33,28,
%T A066659 38,36,58,0,62,34,44,40,39,42,57,54,45,48,55,0,49,50,52,0,94,60,86,66,
%U A066659 64,56,106,0,75,70,63,0,118,0,77,0,74,68,104,0,134,80,92,72,142,78,91
%N A066659 Least k > n such that phi(k) = phi(n), if such k exists; = 0 otherwise.
%H A066659 Paul Tek, <a href="/A066659/b066659.txt">Table of n, a(n) for n = 1..10000</a>
%H A066659 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%t A066659 Table[k = n + 1; While[And[k <= 2 n + 1, EulerPhi@ k != EulerPhi@ n], k++]; Boole[k < 2 n + 1] k, {n, 73}] (* _Michael De Vlieger_, Dec 31 2016 *)
%o A066659 (PARI) a(n) = {my(v = select(x -> x>n, invphi(eulerphi(n)))); if(#v == 0, 0, vecmin(v));} \\ _Amiram Eldar_, Nov 14 2024, using _Max Alekseyev_'s invphi.gp
%Y A066659 Cf. A000010, A043343.
%K A066659 nonn
%O A066659 1,1
%A A066659 _Joseph L. Pe_, Jan 10 2002
%E A066659 More terms from _Vladeta Jovovic_, Jan 12 2002
%E A066659 Typo in data fixed by _Paul Tek_, Sep 20 2015