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 A060663 #13 Nov 18 2024 04:34:38
%S A060663 240,684,744,912,1092,1176,1200,1368,1596,2340,2376,2496,2700,3072,
%T A060663 3348,4212,5460,5520,5586,5642,5712,6000,6160,6264,6804,6864,7068,
%U A060663 7254,7584,7632,7728,8112,8232,8370,8512,8680,8712,8832,8960,9744,9936
%N A060663 Numbers k such that sigma(x) = k has exactly 7 solutions.
%H A060663 Amiram Eldar, <a href="/A060663/b060663.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale)
%H A060663 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%e A060663 240 = sigma(114) = sigma(135) = sigma(158) = sigma(177) = sigma(203) = sigma(209) = sigma(239).
%t A060663 a = Table[ 0, {10000} ]; Do[ s = DivisorSigma[ 1, n ]; If[ s < 10001, a[ [ s ] ]++ ], {n, 1, 10000} ]; Select[ Range[ 10000 ], a[ [ # ] ] == 7 & ]
%t A060663 With[{upto=10000},Select[Tally[DivisorSigma[1,Range[upto]]],#[[2]]==7 && #[[1]] <= upto&]][[All,1]]//Sort (* _Harvey P. Dale_, Jun 22 2019 *)
%o A060663 (PARI) is(k) = invsigmaNum(k) == 7 \\ _Amiram Eldar_, Nov 18 2024, using _Max Alekseyev_'s invphi.gp
%Y A060663 Cf. A000203.
%Y A060663 Number of solutions: A007369 (0), A007370 (1), A007371 (2), A007372 (3), A060660 (4), A060661 (5), A060662 (6), this sequence (7), A060664 (8), A060665 (9), A060666 (10), A060678 (11), A060676 (12).
%K A060663 nonn
%O A060663 1,1
%A A060663 _Robert G. Wilson v_, Apr 18 2001