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 A158275 #14 Nov 21 2022 09:39:03
%S A158275 1,3,2,1,3,6,4,3,1,9,6,2,7,12,6,1,9,3,10,1,8,18,12,6,1,21,2,4,15,18,
%T A158275 16,3,12,27,12,1,19,6,14,9,21,24,22,2,3,36,24,2,1,1
%N A158275 Denominators of antiharmonic means of divisors of n.
%C A158275 Numbers k such that sigma_2(k)/sigma_1(k) = A001157(k)/A000203(k) are integers are in A020487.
%H A158275 Ivan Neretin, <a href="/A158275/b158275.txt">Table of n, a(n) for n = 1..10000</a>
%F A158275 Antiharmonic mean of divisors of number n = Product (p_i^e_i) is sigma_2(n)/sigma_1(n) = A001157(n)/A000203(n) = Product ((p_i^(e_i+1)+1)/(p_i+1)).
%F A158275 a(A020487(n)) = 1. - _Amiram Eldar_, Nov 21 2022
%e A158275 Antiharmonic means of divisors of n>=1: 1, 5/3, 5/2, 3, 13/2, 25/6, ...
%t A158275 Table[Denominator[DivisorSigma[2, n]/DivisorSigma[1, n]], {n, 50}] (* _Ivan Neretin_, May 22 2015 *)
%o A158275 (PARI) a(n) = denominator(sigma(n,2)/sigma(n)); \\ _Amiram Eldar_, Nov 21 2022
%Y A158275 Cf. A001157, A000203, A020487, A158274 (numerators).
%K A158275 nonn,frac
%O A158275 1,2
%A A158275 _Jaroslav Krizek_, Mar 15 2009