login
E.g.f.: x/(1-4*x).
2

%I #18 Jun 03 2022 19:15:47

%S 0,1,8,96,1536,30720,737280,20643840,660602880,23781703680,

%T 951268147200,41855798476800,2009078326886400,104472072998092800,

%U 5850436087893196800,351026165273591808000,22465674577509875712000

%N E.g.f.: x/(1-4*x).

%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=513">Encyclopedia of Combinatorial Structures 513</a>

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

%F 4^(n-1)*n!=n!*A000302(n-1). for n >= 1.

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

%t With[{nn=20},CoefficientList[Series[x/(1-4x),{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Jan 15 2017 *)

%Y A034177 is an essentially identical sequence. - _Philippe Deléham_, Sep 18 2008

%K easy,nonn

%O 0,3

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