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 A318060 #11 Mar 30 2023 16:49:54
%S A318060 1,1,3,1,5,3,7,1,9,10,11,3,13,7,1,1,17,9,19,5,1,22,23,1,25,13,3,7,29,
%T A318060 2,31,4,33,17,35,9,37,19,13,20,41,1,43,11,15,46,47,3,49,25,17,52,53,3,
%U A318060 11,7,19,29,59,1,61,31,3,1,65,66,67,17,23,70
%N A318060 a(n) is the denominator of sigma(sigma(n))/n.
%H A318060 Robert Israel, <a href="/A318060/b318060.txt">Table of n, a(n) for n = 1..10000</a>
%e A318060 For n=2, sigma(sigma(n)) = 4, so a(2) = 1.
%p A318060 seq(denom((numtheory:-sigma@@2)(n)/n),n=1..200); # _Robert Israel_, Aug 15 2018
%t A318060 Table[(DivisorSigma[1,DivisorSigma[1,n]])/n,{n,70}]//Denominator (* _Harvey P. Dale_, Mar 30 2023 *)
%o A318060 (PARI) a(n) = denominator(sigma(sigma(n))/n);
%Y A318060 Cf. A000203 (sigma), A051027.
%Y A318060 Cf. A019278 (where a(n) = 1), A318059 (numerator).
%K A318060 nonn,frac
%O A318060 1,3
%A A318060 _Michel Marcus_, Aug 14 2018