%I A052596
%S A052596 1,1,2,6,48,120,720,5040,40320,362880,3628800,39916800,479001600,
%T A052596 6227020800,87178291200,1307674368000,20922789888000,355687428096000,
%U A052596 6402373705728000,121645100408832000,2432902008176640000
%N A052596 A simple regular expression in a labeled universe.
%H A052596 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=541">
               Encyclopedia of Combinatorial Structures 541</a>
%F A052596 E.g.f.: (-1-x^4+x^5)/(-1+x)
%F A052596 Recurrence: {a(1)=1, a(0)=1, (-1-n)*a(n)+a(n+1), a(3)=6, a(2)=2, a(5)=120, 
               a(4)=48}
%F A052596 n!
%p A052596 spec := [S,{S=Union(Sequence(Z),Prod(Z,Z,Z,Z))},labeled]: seq(combstruct[count](spec,
               size=n), n=0..20);
%Y A052596 Sequence in context: A078537 A145502 A072444 this_sequence A098710 A052614 
               A052688
%Y A052596 Adjacent sequences: A052593 A052594 A052595 this_sequence A052597 A052598 
               A052599
%K A052596 easy,nonn
%O A052596 0,3
%A A052596 encyclopedia(AT)pommard.inria.fr, Jan 25 2000