A052652 - OEIS

%I #13 Apr 18 2017 07:03:58

%S 0,0,0,0,24,240,2880,40320,645120,11612160,232243200,5109350400,

%T 122624409600,3188234649600,89270570188800,2678117105664000,

%U 85699747381248000,2913791410962432000,104896490794647552000

%N E.g.f. x^4/(1-2x).

%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=599">Encyclopedia of Combinatorial Structures 599</a>

%F E.g.f.: -x^4/(-1+2*x)

%F Recurrence: {a(1)=0, a(0)=0, a(2)=0, a(3)=0, (-2*n-2)*a(n)+a(n+1)=0, a(4)=24}

%F 2^(n-4)*n!, n>3.

%p spec := [S,{S=Prod(Z,Z,Z,Z,Sequence(Union(Z,Z)))},labeled]: seq(combstruct[count](spec,size=n), n=0..20);

%t With[{nn=20},CoefficientList[Series[x^4/(1-2x),{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Mar 30 2017 *)

%K easy,nonn

%O 0,5

%A encyclopedia(AT)pommard.inria.fr, Jan 25 2000