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 A307713 #10 Apr 28 2019 23:03:37
%S A307713 2,2,2,2,2,2,2,2,2,3,2,3,2,3,2,2,2,4,4,2,2,3,4,2,3,3,4,2,3,4,2,2,2,5,
%T A307713 2,4,5,5,3,3,3,2,3,2,4,2,3,6,3,4,4,2,6,3,6,6,6,4,3,2,6,6,3,3,6,6,7,3,
%U A307713 3,6,4,6,3,6,7,2,6,4,3,6,4,4,4,4,5,3,7,4,2,8,4,4,4,4,4,3,4,5,6
%N A307713 a(n) = A000010(A307712(n))/A048865(A307712(n)).
%C A307713 1/a(n) is the fraction of primes in the reduced residue system mod A307712(n).
%H A307713 Robert Israel, <a href="/A307713/b307713.txt">Table of n, a(n) for n = 1..600</a>
%e A307713 a(3) = 2 because A307712(3) = 5 and 1/2 of the reduced residue system mod 5 are primes.
%p A307713 g:= proc(n) uses numtheory;
%p A307713 local v;
%p A307713 v:= phi(n)/(pi(n) - nops(factorset(n)));
%p A307713 if v::integer then v fi;
%p A307713 end proc:
%p A307713 map(g, [$3..40000]);
%t A307713 Select[Table[EulerPhi[n]/Count[Prime@ Range@ PrimePi@ n, _?(GCD[#, n] == 1 &)], {n, 3, 25000}], IntegerQ] (* _Michael De Vlieger_, Apr 23 2019 *)
%Y A307713 Cf. A000010, A048865, A307711, A307712.
%K A307713 nonn
%O A307713 1,1
%A A307713 _Robert Israel_, Apr 23 2019