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 A289828 #23 Nov 15 2024 06:59:57
%S A289828 1,3,7,15,25,13,43,51,81,41,121,65,157,129,143,255,289,109,361,187,
%T A289828 301,253,529,193,625,313,487,337,841,241,961,771,661,685,899,433,1369,
%U A289828 1083,937,641,1681,551,1849,881,1147,1013,2209,769,2401,1111,1751,1249,2809,1141,2323,1469,2053,1711
%N A289828 a(n) is the least k such that phi(k) = n*phi(n).
%H A289828 Charles R Greathouse IV, <a href="/A289828/b289828.txt">Table of n, a(n) for n = 1..10000</a>
%H A289828 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%F A289828 a(n) = A015126(n^2).
%F A289828 n^2/log log n << a(n) <= n^2. More specifically (on the lower bound), a(n) > n^2(e^-gamma + o(1))/log log n. - _Charles R Greathouse IV_, Aug 14 2017
%t A289828 With[{s = EulerPhi /@ Range[10^4]}, Table[First@ FirstPosition[s, n EulerPhi@ n], {n, 58}]] (* _Michael De Vlieger_, Aug 14 2017 *)
%o A289828 (PARI) a(n) = my(k=1); while(1, if(eulerphi(k)==n*eulerphi(n), return(k)); k++) \\ _Felix Fröhlich_, Aug 14 2017
%o A289828 (PARI) a(n) = invphiMin(n * eulerphi(n)); \\ _Amiram Eldar_, Nov 15 2024, using _Max Alekseyev_'s invphi.gp
%Y A289828 Cf. A000010, A002618, A015126.
%K A289828 nonn,easy
%O A289828 1,2
%A A289828 _Altug Alkan_, Aug 13 2017