%I A052614
%S A052614 1,1,2,6,48,240,1440,10080,120960,1088640,10886400,119750400,
%T A052614 1916006400,24908083200,348713164800,5230697472000,104613949440000,
%U A052614 1778437140480000,32011868528640000,608225502044160000
%N A052614 A simple regular expression in a labeled universe.
%H A052614 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=559">
               Encyclopedia of Combinatorial Structures 559</a>
%F A052614 E.g.f.: 1/(-1+x)/(-1+x^4)
%F A052614 Recurrence: {a(1)=1, a(0)=1, a(3)=6, a(2)=2, (-61*n-11*n^3-n^4-30-41*n^2)*a(n)+(-n^2-5*n-6)*a(n+1)+(-n-3)*a(n\
               +2)+a(n+4)-a(n+3)}
%F A052614 (Sum(1/16*(2*_alpha+_alpha^2-1)*_alpha^(-1-n), _alpha=RootOf(1+_Z+_Z^2+_Z^3))+1/
               4*n+5/8)*n!
%F A052614 n!*[n/4+1].
%p A052614 spec := [S,{S=Prod(Sequence(Z),Sequence(Prod(Z,Z,Z,Z)))},labeled]: seq(combstruct[count](spec,
               size=n), n=0..20);
%Y A052614 Sequence in context: A072444 A052596 A098710 this_sequence A052688 A052657 
               A092143
%Y A052614 Adjacent sequences: A052611 A052612 A052613 this_sequence A052615 A052616 
               A052617
%K A052614 easy,nonn
%O A052614 0,3
%A A052614 encyclopedia(AT)pommard.inria.fr, Jan 25 2000