%I #13 Apr 18 2017 07:03:59
%S 1,1,10,60,768,9480,161280,2968560,65036160,1568004480,42507763200,
%T 1259454873600,40850693452800,1432712945664000,54168492771993600,
%U 2193096759549696000,94738664609132544000,4347659200973856768000
%N E.g.f. (1-x)/(1-2x-3x^2+3x^3).
%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=611">Encyclopedia of Combinatorial Structures 611</a>
%F E.g.f.: -(-1+x)/(1-2*x-3*x^2+3*x^3)
%F Recurrence: {a(1)=1, a(0)=1, a(2)=10, (3*n^3+18*n^2+33*n+18)*a(n)+(-18-3*n^2-15*n)*a(n+1)+(-2*n-6)*a(n+2)+a(n+3)}
%F Sum(-1/107*(-13-38*_alpha+33*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(1-2*_Z-3*_Z^2+3*_Z^3))*n!
%F a(n) = n!*A052538(n). - _R. J. Mathar_, Nov 27 2011
%p spec := [S,{S=Sequence(Prod(Z,Union(Z,Z,Z,Sequence(Z))))},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
%K easy,nonn
%O 0,3
%A encyclopedia(AT)pommard.inria.fr, Jan 25 2000