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 A072331 #11 Jan 01 2024 13:54:46
%S A072331 3,38,772,21768,786736,34703456,1807726656,108602413184,7392195003136,
%T A072331 562241229891072,47257832090862592,4349969517278922752,
%U A072331 435185983056255725568,47017486048144734052352
%N A072331 a(n) = 2^(n-1) * Sum_{k=0..n} ((n+k)!/(n-k)!)/k!.
%t A072331 Table[2^(n-1) Sum[((n+k)!/(n-k)!)/k!,{k,0,n}],{n,15}] (* _Harvey P. Dale_, May 22 2012 *)
%Y A072331 Cf. A001517.
%K A072331 easy,nonn
%O A072331 1,1
%A A072331 _Benoit Cloitre_, Jul 31 2002
%E A072331 Definition clarified by _Harvey P. Dale_, May 22 2012