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 A357819 #9 Oct 15 2022 07:19:28
%S A357819 1,3,12,4,12,1,8,24,24,72,72,36,252,504,126,504,504,504,2520,840,3360,
%T A357819 10080,10080,10080,2016,2016,2016,2016,10080,10080,5040,1260,5040,
%U A357819 15120,7560,3780,71820,17955,143640,17955,35910,574560,6320160,6320160,6320160,6320160
%N A357819 Denominators of the partial sums of the reciprocals of the Dedekind psi function (A001615).
%C A357819 See A357818 for more details.
%F A357819 a(n) = denominator(Sum_{k=1..n} 1/psi(k)).
%t A357819 psi[n_] := n * Times @@ (1 + 1/Transpose[FactorInteger[n]][[1]]); psi[1] = 1; Denominator[Accumulate[1/Array[psi[#] &, 50]]]
%o A357819 (PARI) f(n) = n * sumdivmult(n, d, issquarefree(d)/d); \\ A001615
%o A357819 a(n) = denominator(sum(k=1, n, 1/f(k))); \\ _Michel Marcus_, Oct 15 2022
%Y A357819 Cf. A001615, A173290, A357818 (numerators).
%Y A357819 Similar sequences: A048049, A104529, A212718.
%K A357819 nonn,frac
%O A357819 1,2
%A A357819 _Amiram Eldar_, Oct 14 2022