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 A341523 #9 Feb 17 2021 20:26:35
%S A341523 0,0,0,0,0,2,0,0,0,1,0,2,0,1,1,0,0,1,0,1,0,1,0,3,0,1,0,3,0,2,0,0,1,1,
%T A341523 0,0,0,1,0,2,0,2,0,2,1,1,0,2,0,0,1,1,0,2,0,3,0,1,0,3,0,1,0,0,0,2,0,1,
%U A341523 1,1,0,1,0,1,0,2,0,2,0,1,0,1,0,3,0,1,1,2,0,3,1,2,0,1,1,3,0,0,1,0,0,2,0,1,1
%N A341523 Number of prime factors (with multiplicity) shared by n and sigma(n): a(n) = bigomega(gcd(n, sigma(n))).
%H A341523 Antti Karttunen, <a href="/A341523/b341523.txt">Table of n, a(n) for n = 1..65537</a>
%H A341523 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A341523 a(n) = A001222(A009194(n)).
%F A341523 a(n) = A001222(n) - A341524(n).
%F A341523 a(A003961(n)) = A341519(n).
%t A341523 Table[PrimeOmega[GCD[n, DivisorSigma[1, n]]], {n, 1, 100}] (* _Amiram Eldar_, Feb 17 2021 *)
%o A341523 (PARI) A341523(n) = bigomega(gcd(n, sigma(n)));
%Y A341523 Cf. A000203, A003961, A009194, A014567 (positions of zeros), A341519, A341524.
%K A341523 nonn
%O A341523 1,6
%A A341523 _Antti Karttunen_, Feb 17 2021