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