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 A348985 #11 Nov 11 2021 21:38:26
%S A348985 1,1,1,7,1,1,1,5,13,1,1,7,1,1,1,31,1,13,1,7,1,1,1,5,31,1,5,7,1,1,1,7,
%T A348985 1,1,1,91,1,1,1,5,1,1,1,7,13,1,1,31,57,31,1,7,1,5,1,5,1,1,1,7,1,1,13,
%U A348985 127,1,1,1,7,1,1,1,65,1,1,31,7,1,1,1,31,121,1,1,7,1,1,1,5,1,13,1,7,1,1,1,7,1,57,13
%N A348985 Numerator of ratio sigma(n) / A325973(n), where A325973 is the arithmetic mean of {sum of squarefree divisors} and {sum of unitary divisors}.
%C A348985 This is not multiplicative. The first point where a(m*n) = a(m)*a(n) does not hold for coprime m and n is 108 = 4*27, where a(108) = 70 <> 35 = 7*5 = a(4)*(27).
%H A348985 Antti Karttunen, <a href="/A348985/b348985.txt">Table of n, a(n) for n = 1..20000</a>
%H A348985 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A348985 a(n) = A000203(n) / A348984(n) = sigma(n) / gcd(sigma(n), A325973(n)).
%t A348985 f1[p_, e_] := p + 1; f2[p_, e_] := p^e + 1; s[1] = 1; s[n_] := (Times @@ f1 @@@ (f = FactorInteger[n]) + Times @@ f2 @@@ f)/2; a[n_] := Numerator[DivisorSigma[1, n]/s[n]]; Array[a, 100] (* _Amiram Eldar_, Nov 06 2021 *)
%o A348985 (PARI)
%o A348985 A325973(n) = (1/2)*sumdiv(n, d, d*(issquarefree(d) + (1==gcd(d, n/d))));
%o A348985 A348985(n) = { my(s=sigma(n)); (s/gcd(s, A325973(n))); };
%Y A348985 Cf. A000203, A048250, A034448, A325973, A325974, A348984, A348986 (denominators).
%Y A348985 Differs from A348048 for the first time at n=108, where a(108) = 70, while A348048(108) = 35.
%Y A348985 Cf. also A348948.
%K A348985 nonn,frac
%O A348985 1,4
%A A348985 _Antti Karttunen_, Nov 06 2021