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 A336388 #7 Jul 26 2020 09:50:52
%S A336388 0,0,0,0,0,2,0,0,0,1,0,1,0,1,1,0,0,1,0,1,0,1,0,2,0,1,0,2,0,2,0,0,1,1,
%T A336388 0,0,0,1,0,2,0,2,0,1,1,1,0,1,0,0,1,1,0,2,0,1,0,1,0,2,0,1,0,0,0,2,0,1,
%U A336388 1,1,0,1,0,1,0,1,0,2,0,1,0,1,0,2,0,1,1,1,0,2,1,1,0,1,1,2,0,0,1,0,0,2,0,1,1
%N A336388 Number of prime divisors of sigma(n) that divide n; a(1) = 0.
%H A336388 Antti Karttunen, <a href="/A336388/b336388.txt">Table of n, a(n) for n = 1..65537</a>
%H A336388 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A336388 a(n) = Sum_{p over distinct primes dividing sigma(n)} [p|n], where [ ] is the Iverson bracket, giving in this case 1 only if p divides n, and 0 otherwise.
%o A336388 (PARI) A336388(n) = if(1==n,0,#select(p -> !(n%p), factor(sigma(n))[, 1]));
%Y A336388 Cf. also A173438, A336352, A336387.
%K A336388 nonn
%O A336388 1,6
%A A336388 _Antti Karttunen_, Jul 25 2020