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 A074949 #12 Jan 31 2021 02:59:35
%S A074949 1,1,6,6,60,60,140,420,2520,2520,27720,27720,360360,360360,72072,
%T A074949 360360,12252240,12252240,77597520,46558512,25865840,33256080,
%U A074949 118982864,5354228880,8923714800,3824449200,80313433200,80313433200,2329089562800
%N A074949 Denominators of Sum_{k=1..n} 1/lcm(n,k).
%H A074949 Amiram Eldar, <a href="/A074949/b074949.txt">Table of n, a(n) for n = 1..2308</a>
%e A074949 1, 1, 5/6, 5/6, 37/60, 47/60, 69/140, 263/420, 1321/2520, 1429/2520, ...
%p A074949 A074949:=proc(n) local i: RETURN(denom(add(1/ilcm(n,i),i=1..n))): end; seq(A074949(n),n=1..30); # C. Ronaldo
%t A074949 a[n_] := Denominator @ Sum[1/LCM[k, n], {k, 1, n}]; Array[a, 30] (* _Amiram Eldar_, Jan 31 2021 *)
%o A074949 (PARI) a(n)=denominator(sum(i=1,n,1/lcm(n,i)))
%Y A074949 Cf. A074947 (numerators).
%K A074949 easy,frac,nonn
%O A074949 1,3
%A A074949 _Benoit Cloitre_, Oct 05 2002