%I #15 Jan 20 2024 16:59:15
%S 2,2,4,18,48,240,1440,10080,80640,725760,7257600,79833600,958003200,
%T 12454041600,174356582400,2615348736000,41845579776000,
%U 711374856192000,12804747411456000,243290200817664000
%N Expansion of e.g.f. (2+x^3-x^4)/(1-x).
%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=574">Encyclopedia of Combinatorial Structures 574</a>
%F E.g.f.: (-2+x^4-x^3)/(-1+x).
%F Recurrence: {(-1-n)*a(n)+a(n+1)=0, a(2)=4, a(1)=2, a(0)=2, a(4)=48, a(3)=18}
%F 2*n!, n != 3.
%p spec := [S,{S=Union(Sequence(Z),Sequence(Z),Prod(Z,Z,Z))},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
%t With[{nn=20},CoefficientList[Series[(2+x^3-x^4)/(1-x),{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Feb 03 2015 *)
%K easy,nonn
%O 0,1
%A encyclopedia(AT)pommard.inria.fr, Jan 25 2000