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 A064647 #13 Feb 08 2025 04:52:02
%S A064647 2,3,10,105,770,15015,170170,4849845,6760390,3234846615,200560490130,
%T A064647 72752334655,4680773285034,284407855036305,614889782588491410,
%U A064647 465559406817000639,44715356980330526490,19548063559901161830545
%N A064647 Denominators of partial sums of reciprocals of primorial numbers.
%e A064647 For n = 5, Sum_{j=1..5} 1/A002110(j) = 1/2 + 1/6 + 1/30 + 1/210 + 1/2310 = (1155 + 385 + 77 + 11 + 1)/2310 = 1629/2310 = 543/770, so a(5) = 770.
%t A064647 q[x_] := Apply[Times, Table[Prime[j], {j, 1, x}]]; a[n_] := Denominator[Apply[Plus, Table[1/q[w], {w, 1, n}]]]; Array[a, 18]
%o A064647 (PARI) list(lim) = {my(s = 0, pr = 1); forprime(p = 1, lim, pr *= p; s += 1/pr; print1(denominator(s), ", "));} \\ _Amiram Eldar_, Feb 08 2025
%Y A064647 Cf. A002110, A064646 (numerators).
%K A064647 frac,nonn
%O A064647 1,1
%A A064647 _Labos Elemer_, Oct 04 2001