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 A060660 #9 Nov 18 2024 05:24:58
%S A060660 96,120,180,312,372,420,434,456,540,546,560,624,702,728,798,816,930,
%T A060660 1064,1120,1170,1404,1632,1638,1674,1710,1776,1792,1944,2100,2240,
%U A060660 2544,2560,2664,2760,2800,2844,2856,2940,2952,3000,3040,3048,3060,3080,3096
%N A060660 Numbers k such that sigma(x) = k has exactly 4 solutions.
%H A060660 Amiram Eldar, <a href="/A060660/b060660.txt">Table of n, a(n) for n = 1..10000</a>
%H A060660 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%e A060660 96 = sigma(42) = sigma(62) = sigma(69) = sigma(77).
%t A060660 a = Table[ 0, {5000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 5001, a[ [ s ] ]++ ], {n, 1, 5000} ]; Select[ Range[ 5000 ], a[ [ # ] ] == 4 & ]
%o A060660 (PARI) is(k) = invsigmaNum(k) == 4 \\ _Amiram Eldar_, Nov 17 2024, using _Max Alekseyev_'s invphi.gp
%Y A060660 Cf. A000203.
%Y A060660 Number of solutions: A007369 (0), A007370 (1), A007371 (2), A007372 (3), this sequence (4), A060661 (5), A060662 (6), A060663 (7), A060664 (8), A060665 (9), A060666 (10), A060678 (11), A060676 (12).
%K A060660 nonn
%O A060660 1,1
%A A060660 _Robert G. Wilson v_, Apr 18 2001