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 A303613 #13 Apr 27 2018 10:32:10
%S A303613 1,2,8,44,300,2408,22056,225824,2547352,31322640,416442016,5948450912,
%T A303613 90815006528,1475513165184,25419300628160,462839142264960,
%U A303613 8882065110092000,179190173518717120,3791700201187720960,83977684252758211200,1942984028971973710720
%N A303613 a(n) = [x^n] (1/6 * Sum_{k=0..n} (k+3)!*x^k)^(1/2).
%H A303613 Seiichi Manyama, <a href="/A303613/b303613.txt">Table of n, a(n) for n = 0..447</a>
%o A303613 (PARI) N=66; x='x+O('x^N); Vec((1/3!*sum(k=0, N, (k+3)!*x^k))^(1/2))
%Y A303613 Cf. A001715, A303568.
%K A303613 nonn
%O A303613 0,2
%A A303613 _Seiichi Manyama_, Apr 27 2018