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 A010796 a(n)=n!*(n+1)!/2. 6

%I

%S 1,6,72,1440,43200,1814400,101606400,7315660800,658409472000,

%T 72425041920000,9560105533440000,1491376463216640000,

%U 271430516305428480000,57000408424139980800000

%N a(n)=n!*(n+1)!/2.

%H Vincenzo Librandi, <a href="/A010796/b010796.txt">Table of n, a(n) for n = 1..200</a>

%H <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>

%F E.g.f.: (hypergeom([1, 2], [], x)-1)/2.

%p a:=array(0...14): a[0]:=0: a[1]:=1: print(1,a[1]); for i from 2 to 14 do a[i]:= a[i-1]*(i)*(i+1): print(i,a[i]); od: - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 27 2007

%t s=1;lst={s};Do[s+=(s*=n)*n;AppendTo[lst, s], {n, 2, 5!, 1}];lst [From _Vladimir Joseph Stephan Orlovsky_, Nov 15 2008]

%t Table[n! (n + 1)! / 2, {n, 1, 20}] (* _Vincenzo Librandi_, Jun 11 2013 *)

%o (MAGMA) [Factorial(n)* Factorial(n+1) / 2: n in [1..20]]; // _Vincenzo Librandi_, Jun 11 2013

%Y a(n)=A078740(n, 2), first column of (3, 2)-Stirling2 array.

%Y Equals 2^(n-1) * A006472(n+1).

%Y Column 2 in triangle A009963.

%Y Equals (1/2) A010790.

%K nonn,easy,changed

%O 1,2

%A _N. J. A. Sloane_.

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