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 A007609 #43 Apr 15 2020 02:23:56
%S A007609 1,3,4,6,7,8,12,12,13,14,15,18,18,20,24,24,24,28,30,31,31,32,32,36,38,
%T A007609 39,40,42,42,42,44,48,48,48,54,54,56,56,57,60,60,60,62,63,68,72,72,72,
%U A007609 72,72,74,78,80,80,84,84,84,90,90,90,91,93,96,96,96,96,98,98
%N A007609 Values taken by the sigma function A000203, listed with multiplicity and in ascending order.
%C A007609 A175192(a(n)) = 1, A054973(a(n)) >= 1. - _Jaroslav Krizek_, Mar 01 2010
%C A007609 a(n) is the median of the values of A000203(m) from m=1 to m=2n-1. (This needs confirmation as it relies on the assumption that A000203(n) is always bigger than the median of the values A000203(x) from x=1 to x=n.) - _Chayim Lowen_, May 27 2015
%H A007609 T. D. Noe, <a href="/A007609/b007609.txt">Table of n, a(n) for n = 1..10000</a>
%F A007609 a(n) = sigma(A085790(n)). - _Jinyuan Wang_, Apr 15 2020
%p A007609 sort(select(`<=`,map(numtheory:-sigma,[$1..1000]),1001)); # _Robert Israel_, Jun 04 2015
%t A007609 terms = 68; ClearAll[t]; t[k_] := t[k] = Sort[ Table[ DivisorSigma[1, n], {n, 1, k*terms}]][[1 ;; terms]]; t[k = 2]; While[t[k] != t[k-1], k++]; t[k] (* _Jean-François Alcover_, Nov 21 2012 *)
%t A007609 With[{nn=80},Take[Sort[DivisorSigma[1,Range[nn*100]]],nn]] (* _Harvey P. Dale_, Mar 09 2016 *)
%o A007609 (PARI) list(lim)=select(k->k<=lim,Set(apply(sigma,[1..lim\1]))) \\ _Charles R Greathouse IV_, Mar 09 2014
%Y A007609 Cf. A000203, A002191 (duplicates removed), A007368, A085790.
%K A007609 nonn,easy,nice
%O A007609 1,2
%A A007609 _Walter Nissen_