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 A336554 #15 Dec 27 2024 04:10:42 %S A336554 1,135,891,1521,3375,5733,10935,11907,41067,43875,84375,89667,92781, %T A336554 98865,107811,108927,154791,185625,200655,216513,226233,273375,274625, %U A336554 287469,307125,336141,416745,448335,480249,544635,557375,570375,590625,627669,628849,648675,692055,823875,885735,931095,968877,1071875,1108809,1131165 %N A336554 Odd numbers k such that rad(k) divides sigma(k). %C A336554 Only a minority of terms seem to be also in A228058: 5733, 92781, 2069613, 3341637, 4179357, 5929605, 60998353, 67637349, 89162541 among the first 216, the five of them which occur also in A263983. %C A336554 Question: Is the intersection with A336553 empty? %H A336554 Amiram Eldar, <a href="/A336554/b336554.txt">Table of n, a(n) for n = 1..1200</a> (terms 1..216 from Antti Karttunen) %H A336554 <a href="/index/O#opnseqs">Index entries for sequences where odd perfect numbers must occur, if they exist at all</a>. %o A336554 (PARI) isA336554(n) = if(!(n%2),0,!(sigma(n) % factorback(factorint(n)[, 1]))); %Y A336554 Odd terms of A175200. %Y A336554 Cf. A000203, A007947, A228058, A263983. %Y A336554 Cf. also A336553. %K A336554 nonn %O A336554 1,2 %A A336554 _Antti Karttunen_, Jul 28 2020