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 A243045 #9 Feb 18 2023 08:09:20 %S A243045 0,0,6,12,0,12,0,24,18,15,0,60,0,0,60,48,0,36,0,60,42,0,0,168,0,0,54, %T A243045 84,0,120,0,96,66,0,210,180,0,0,78,360,0,105,0,132,180,0,0,336,0,75, %U A243045 102,156,0,108,66,168,114,0,0,660,0,0,504,192,0,132,0,204,138,420,0,504 %N A243045 Largest number k such that k*n/(k+n) and k*n/(k-n) are integers or 0 if no such number exists. %H A243045 Antti Karttunen, <a href="/A243045/b243045.txt">Table of n, a(n) for n = 1..10080</a> %e A243045 k*3/(k-3) and k*3/(k+3) are integers only for k=6. Thus since 6 is the largest k-value, a(3) = 6. %o A243045 (PARI) a(n)=for(k=-n*(n+1),0,if(-k!=n,if((-k*n)/(-k+n)==0&&(-k*n)/(-k-n)==0,return(-k)))) %o A243045 n=1;while(n<100,print1(a(n),", ");n+=1) %Y A243045 Cf. A243017, A243046, A243047 (positions of 0's), A360120 (their characteristic function). %K A243045 nonn,look %O A243045 1,3 %A A243045 _Derek Orr_, May 29 2014