%I A052764
%S A052764 0,1,8,144,4096,160000,7962624,481890304,34359738368,2821109907456,
%T A052764 262144000000000,27197360938418176,3116402981210161152,
%U A052764 390877006486250192896,53265296773103187132416
%N A052764 A simple grammar.
%H A052764 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=721">
               Encyclopedia of Combinatorial Structures 721</a>
%F A052764 E.g.f.: -1/4*LambertW(-4*x)
%p A052764 spec := [S,{B=Set(S),S=Prod(Z,B,B,B,B)},labeled]: seq(combstruct[count](spec,
               size=n), n=0..20);
%Y A052764 Sequence in context: A134492 A067421 A124059 this_sequence A024284 A024285 
               A111687
%Y A052764 Adjacent sequences: A052761 A052762 A052763 this_sequence A052765 A052766 
               A052767
%K A052764 easy,nonn
%O A052764 0,3
%A A052764 encyclopedia(AT)pommard.inria.fr, Jan 25 2000