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 A060675 #14 Nov 17 2024 07:20:25
%S A060675 160,168,352,448,816,928,972,1024,1176,1848,2464,3040,3808,4152,4440,
%T A060675 4512,4736,4944,5104,5152,5160,5304,5952,6408,6656,6672,6784,7648,
%U A060675 8384,8704,8904,10432,10528,10624,11000,11008,11456,11776,12048,12416,13024,13032
%N A060675 Numbers k such that phi(x) = k has exactly 12 solutions.
%H A060675 Amiram Eldar, <a href="/A060675/b060675.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from T. D. Noe)
%H A060675 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%e A060675 160 = phi(187) = phi(205) = phi(328) = phi(352) = phi(374) = phi(400) = phi(410) = phi(440) = phi(492) = phi(528) = phi(600) = phi(660).
%t A060675 a = Table[ 0, {15000} ]; Do[ p = EulerPhi[ n ]; If[ p < 15001, a[ [ p ] ]++ ], {n, 1, 60000} ]; Select[ Range[ 15000 ], a[ [ # ] ] == 12 & ]
%t A060675 Union[Transpose[Select[Tally[EulerPhi[Range[100000]]],#[[2]]==12&]][[1]]] (* _Harvey P. Dale_, Oct 05 2015 *)
%o A060675 (PARI) is(n)=sum(i=1,n,eulerphi(i)==n)==12 \\ _Charles R Greathouse IV_, Mar 03 2014
%o A060675 (PARI) is(k) = invphiNum(k) == 12 \\ _Amiram Eldar_, Nov 17 2024, using _Max Alekseyev_'s invphi.gp
%Y A060675 Cf. A000010.
%Y A060675 Number of solutions: A007617 (0), A007366 (2), A007367 (3), A060667 (4), A060668 (5), A060669 (6), A060670 (7), A060671 (8), A060672 (9), A060673 (10), A060674 (11), this sequence (12).
%K A060675 nonn
%O A060675 1,1
%A A060675 _Robert G. Wilson v_, Apr 18 2001