%I A052914
%S A052914 1,0,0,1,3,1,2,7,12,10,19,41,61,76,135,240,356,521,879,1445,2198,3407,
%T A052914 5568,8898,13811,21797,35017,55488,87111,138100,220028,348081,549427,
%U A052914 871433,1383370,2188903,3463028,5490410,8703187,13777281,21815941
%N A052914 A simple regular expression.
%H A052914 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=896">
               Encyclopedia of Combinatorial Structures 896</a>
%F A052914 G.f.: -(-1+x)/(1-x-2*x^4+2*x^5-x^3)
%F A052914 Recurrence: {a(1)=0, a(0)=1, a(2)=0, a(3)=1, a(4)=3, 2*a(n)-2*a(n+1)-a(n+2)-a(n+4)+a(n+5)}
%F A052914 Sum(-1/19913*(-418-4709*_alpha+599*_alpha^2+1048*_alpha^3+542*_alpha^4)*_alpha^(-1-n), 
               _alpha=RootOf(1-_Z-2*_Z^4+2*_Z^5-_Z^3))
%p A052914 spec := [S,{S=Sequence(Prod(Union(Sequence(Z),Z,Z),Z,Z,Z))},unlabeled]: 
               seq(combstruct[count](spec,size=n), n=0..20);
%Y A052914 Sequence in context: A135338 A084602 A100888 this_sequence A131671 A060750 
               A086961
%Y A052914 Adjacent sequences: A052911 A052912 A052913 this_sequence A052915 A052916 
               A052917
%K A052914 easy,nonn
%O A052914 0,5
%A A052914 encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E A052914 More terms from James A. Sellers (sellersj(AT)math.psu.edu), May 06 2000