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 A060664 #10 Nov 18 2024 03:46:54
%S A060664 336,432,672,756,840,1536,1620,1764,1848,2280,2394,2604,2808,3264,
%T A060664 4080,4480,4860,5328,6528,6624,7128,8316,8568,8880,10608,11040,11448,
%U A060664 12288,12420,12636,13176,13200,13248,13536,13860,14196,14208,14448,14700
%N A060664 Numbers k such that sigma(x) = k has exactly 8 solutions.
%H A060664 Robert Israel, <a href="/A060664/b060664.txt">Table of n, a(n) for n = 1..10000</a>
%H A060664 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%e A060664 336 = sigma(132) = sigma(140) = sigma(182) = sigma(188) = sigma(195) = sigma(249) = sigma(287) = sigma(299).
%p A060664 N:= 30000: # to get terms <= N
%p A060664 V:= Vector(N):
%p A060664 for k from 1 to N-1 do
%p A060664 t:= numtheory:-sigma(k);
%p A060664 if t <= N then V[t]:= V[t]+1 fi
%p A060664 od:
%p A060664 select(t -> V[t]=8, [$1..N]); # _Robert Israel_, Sep 22 2019
%t A060664 a = Table[ 0, {20000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 20001, a[ [ s ] ]++ ], {n, 1, 20000} ]; Select[ Range[ 20000 ], a[ [ # ] ] == 8 & ]
%o A060664 (PARI) is(k) = invsigmaNum(k) == 8 \\ _Amiram Eldar_, Nov 18 2024, using _Max Alekseyev_'s invphi.gp
%Y A060664 Cf. A000203.
%Y A060664 Number of solutions: A007369 (0), A007370 (1), A007371 (2), A007372 (3), A060660 (4), A060661 (5), A060662 (6), A060663 (7), this sequence (8), A060665 (9), A060666 (10), A060678 (11), A060676 (12).
%K A060664 nonn
%O A060664 1,1
%A A060664 _Robert G. Wilson v_, Apr 18 2001