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 A063885 #8 Sep 10 2019 09:57:40 %S A063885 24,1536,1631,47360,82458 %N A063885 z(sigma(n)) = 2n, where z(n) = A048146. %o A063885 (PARI) u(n) = sumdiv(n,d, if(gcd(d,n/d)==1,d)); %o A063885 z(n) = sigma(n)-u(n); %o A063885 for(n=1,10^7, if(z(sigma(n))==2*n,print1(n, ", "))) %Y A063885 Cf. A000203, A034448, A048146, A019284. %K A063885 nonn,more %O A063885 1,1 %A A063885 _Jason Earls_, Aug 28 2001