%I #11 Apr 18 2017 07:03:59
%S 0,0,0,0,24,240,720,5040,40320,362880,3628800,39916800,479001600,
%T 6227020800,87178291200,1307674368000,20922789888000,355687428096000,
%U 6402373705728000,121645100408832000,2432902008176640000
%N E.g.f. x^4*(1+x-x^2)/(1-x).
%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=610">Encyclopedia of Combinatorial Structures 610</a>
%F E.g.f.: x^4*(-x+x^2-1)/(-1+x)
%F Recurrence: {a(1)=0, a(0)=0, a(2)=0, (-1-n)*a(n)+a(n+1)=0, a(3)=0, a(4)=24, a(6)=720, a(5)=240}
%F n! for n >= 4.
%p spec := [S,{S=Prod(Z,Z,Z,Z,Union(Z,Sequence(Z)))},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
%K easy,nonn
%O 0,5
%A encyclopedia(AT)pommard.inria.fr, Jan 25 2000