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 A064889 #11 Mar 18 2018 09:42:58
%S A064889 1,2,3,4,30,420,840,1260,9240,9009,240240,471240,232792560,535422888,
%T A064889 26771144400,181704600,4822131600,36100888223400,3702655202400,
%U A064889 76327592243760,737576396429600,362291852261631600,6416241209619040800
%N A064889 Denominators of partial sums of reciprocals of A051451 (A051451 includes lcm(1,...,x), x=power of prime from A000961 and also contains 1).
%F A064889 a(n) = denominator(Sum_{k=1..n} 1/A051451(k)).
%e A064889 n=6, sum = (1/1) + (1/2) + (1/6) + (1/12) + (1/60) + (1/420) = 743/420, the denominator = a(6) = 743. Remark: If 1 is omitted from A051451, the denominators of partial sums of reciprocals do not change; however, numerators are changing, not compatible with these denominators (see A064888).
%Y A064889 Cf. A051451, A003418, A000961, A064857, A064858, A064859, A064888, A064890.
%K A064889 frac,nonn
%O A064889 1,2
%A A064889 _Labos Elemer_, Oct 11 2001