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 A303565 #13 May 02 2018 04:39:23
%S A303565 1,2,2,10,18,202,418,8762,18546,648842,1361090,72858394,150831762,
%T A303565 11533704106,23631529186,2447950210490,4980921068466,671176131216458,
%U A303565 1359534955872002,230971485534437722,466475222145987282,97492025362288590058,196500782158151756578
%N A303565 a(n) = [x^n] (Sum_{k=0..n} k!*x^k)/(Sum_{k=0..n} k!*(-x)^k).
%H A303565 Seiichi Manyama, <a href="/A303565/b303565.txt">Table of n, a(n) for n = 0..450</a>
%F A303565 a(n) ~ 4*(n-1)! if n is even and a(n) ~ 2*n! if n is odd. - _Vaclav Kotesovec_, May 02 2018
%o A303565 (PARI) N=66; x='x+O('x^N); Vec(sum(k=0, N, k!*x^k)/sum(k=0, N, k!*(-x)^k))
%Y A303565 Cf. A303566.
%K A303565 nonn
%O A303565 0,2
%A A303565 _Seiichi Manyama_, Apr 26 2018