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 A009213 #11 May 12 2025 14:57:47
%S A009213 1,1,2,1,2,2,2,4,3,4,2,2,2,2,4,1,2,6,2,2,4,2,2,8,1,4,2,6,2,8,2,2,4,4,
%T A009213 4,3,2,2,4,8,2,4,2,2,6,2,2,2,3,2,4,6,2,2,4,8,4,4,2,4,2,2,6,1,4,4,2,2,
%U A009213 4,8,2,12,2,4,2,6,4,8,2,2,1,4,2,12,4,2,4,8,2,12,4,2,4,2,4,4,2,6,6,1,2,8,2,8,8
%N A009213 a(n) = gcd(d(n), phi(n)), where d is the number of divisors of n (A000005) and phi is Euler's totient function (A000010).
%H A009213 Antti Karttunen, <a href="/A009213/b009213.txt">Table of n, a(n) for n = 1..65537</a>
%t A009213 Table[GCD[DivisorSigma[0,n],EulerPhi[n]],{n,110}] (* _Harvey P. Dale_, May 12 2025 *)
%o A009213 (PARI) A009213(n) = gcd(numdiv(n), eulerphi(n)); \\ _Antti Karttunen_, Sep 07 2018
%Y A009213 Cf. A000005, A000010,
%Y A009213 Cf. also A009191, A009195, A009223, A318459.
%K A009213 nonn
%O A009213 1,3
%A A009213 _David W. Wilson_