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 A347247 #8 Aug 30 2021 09:38:13 %S A347247 1,9,18,25,27,36,45,49,50,54,63,72,75,81,90,98,99,100,108,117,121,125, %T A347247 126,135,144,147,150,162,169,175,180,196,198,200,216,225,234,242,243, %U A347247 245,250,252,270,275,288,289,294,300,315,324,325,338,350,360,361,363,375,392,396,400,405,425,432,441,450,468,475 %N A347247 Numbers k such that the greatest prime factor of A000593(k) [the sum of their odd divisors] is at least as large as the greatest prime factor of k itself. %C A347247 The initial 1 is included on the grounds that A006530(1) = 1 and A000593(1) = 1. After 1, if k is included as a term, then also 2*k is present. %C A347247 A038838(27) = 153 is the first term of A038838 not present here. %Y A347247 Cf. A000593, A006530, A347246 (characteristic function), A347248 (complement). %Y A347247 Apart from the initial 1, a subsequence of A347242. %Y A347247 Cf. also A038838. %K A347247 nonn %O A347247 1,2 %A A347247 _Antti Karttunen_, Aug 28 2021