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 A293459 #13 Sep 21 2019 08:26:24
%S A293459 1,1,7,385,3628921,1216452311762688721,
%T A293459 10333147966386144929717742279694909445041,
%U A293459 5989285834984945898036392571843137173092920925318860392502631168811983977451725959000900501504040321
%N A293459 Denominator of probability that a permutation of elements of some subset of set {1,2..n} is a permutation of elements of some set of the form 1..k, k <= n.
%H A293459 Amiram Eldar, <a href="/A293459/b293459.txt">Table of n, a(n) for n = 1..10</a>
%t A293459 a[n_] := Denominator[Sum[k!, {k, 0, n}]/Sum[Binomial[n, k]!, {k, 0, n}]]; Array[a, 8] (* _Amiram Eldar_, Sep 21 2019 *)
%o A293459 (PARI) a(n) = denominator(sum(k=0, n, k!)/sum(k=0, n, binomial(n,k)!)); \\ _Michel Marcus_, Oct 12 2017
%Y A293459 Cf. A293458(numerators).
%K A293459 nonn,frac
%O A293459 1,3
%A A293459 _Vladimir Shevelev_, Oct 09 2017
%E A293459 More terms from _Peter J. C. Moses_, Oct 09 2017