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 A374903 #8 Jul 23 2024 20:46:40 %S A374903 1,2,2,1,2,4,2,2,1,4,2,1,2,4,4,1,2,1,2,1,4,4,2,4,1,4,2,1,2,8,2,2,4,4, %T A374903 4,1,2,4,4,4,2,8,2,1,1,4,2,2,1,1,4,1,2,4,4,4,4,4,2,2,2,4,1,1,4,8,2,1, %U A374903 4,8,2,1,2,4,1,1,4,8,2,2,1,4,2,2,4,4,4 %N A374903 Denominator of the mean number of divisors of the divisors of n. %H A374903 Amiram Eldar, <a href="/A374903/b374903.txt">Table of n, a(n) for n = 1..10000</a> %F A374903 a(A374904(n)) = 1. %F A374903 a(A374905(n)) = 1. %e A374903 For n = 2, n has 2 divisors, 1 and 2. Their numbers of divisors are tau(1) = 1 and tau(2) = 2, and their mean number of divisors is (1 + 2)/2 = 3/2. Therefore a(2) = denominator(3/2) = 2. %t A374903 f[p_, e_] := (e + 2)/2; a[1] = 1; a[n_] := Denominator[Times @@ f @@@ FactorInteger[n]]; Array[a, 100] %o A374903 (PARI) a(n) = denominator(vecprod(apply(x -> x/2 +1, factor(n)[, 2]))); %Y A374903 Cf. A374902 (numerators), A374904, A374905. %K A374903 nonn,easy,frac %O A374903 1,2 %A A374903 _Amiram Eldar_, Jul 23 2024