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 A331019 #12 Jan 09 2020 11:52:04 %S A331019 1,15,1,8,1,144,1,16,1,1,1,8,1,255,3,16,1,12,1,2,7,1,1,288,1,18,21,8, %T A331019 1,84,1,13,1,11,1,4096,1,4,3,270,1,2448,1,2,3,1,1,16,1,420,3,1,1,124, %U A331019 3,16,3,128,1,616,1,85,3,16,1,1,1,8,3,1,1,32,1,64 %N A331019 a(n) is the least k such that the denominator(sigma(sigma(k*n))/(k*n)) equals n. %C A331019 a(n) is the least k such that the A318060(k*n) equals n. %H A331019 Ray Chandler, <a href="/A331019/b331019.txt">Table of n, a(n) for n = 1..10000</a> %F A331019 a(n) = A331033(n)/n. %o A331019 (PARI) a(n) = my(k=n); while (denominator(sigma(sigma(k))/k) != n, k+=n); k/n; %Y A331019 Cf. A000203 (sigma), A051027 (sigma(sigma)), A318060. %Y A331019 Cf. A019278, A330598, A331033. %K A331019 nonn %O A331019 1,2 %A A331019 _Ray Chandler_, Jan 09 2020