%I A052626
%S A052626 3,4,12,60,432,4080,47520,655200,10402560,186520320,3723148800,
%T A052626 81829440000,1962948556800,51024208435200,1428503479603200,
%U A052626 42852489039360000,1371237803679744000,46621373950255104000
%N A052626 A simple regular expression in a labeled universe.
%H A052626 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=572">
               Encyclopedia of Combinatorial Structures 572</a>
%F A052626 E.g.f.: -(-3+5*x)/(-1+2*x)/(-1+x)
%F A052626 Recurrence: {a(0)=3, a(1)=4, (2*n^2+6*n+4)*a(n)+(-6-3*n)*a(n+1)+a(n+2)}
%F A052626 (2^n+2)*n!
%p A052626 spec := [S,{S=Union(Sequence(Z),Sequence(Z),Sequence(Union(Z,Z)))},labeled]: 
               seq(combstruct[count](spec,size=n), n=0..20);
%Y A052626 Sequence in context: A079154 A101716 A109771 this_sequence A122903 A059792 
               A018930
%Y A052626 Adjacent sequences: A052623 A052624 A052625 this_sequence A052627 A052628 
               A052629
%K A052626 easy,nonn
%O A052626 0,1
%A A052626 encyclopedia(AT)pommard.inria.fr, Jan 25 2000