%I A052824
%S A052824 0,0,2,6,34,220,1808,17388,194724,2478096,35418192,561533280,
%T A052824 9785418432,185921027136,3825633439392,84756646285920,
%U A052824 2011657535668128,50924796197369088,1369659967551038976
%N A052824 A simple grammar: cycles of pairs of cycles.
%H A052824 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=789">
               Encyclopedia of Combinatorial Structures 789</a>
%F A052824 E.g.f.: ln(-1/(-1+ln(-1/(-1+x))^2))
%p A052824 spec := [S,{B=Cycle(Z),C=Prod(B,B),S=Cycle(C)},labeled]: seq(combstruct[count](spec,
               size=n), n=0..20);
%Y A052824 Sequence in context: A003499 A018953 A009199 this_sequence A019029 A019032 
               A108424
%Y A052824 Adjacent sequences: A052821 A052822 A052823 this_sequence A052825 A052826 
               A052827
%K A052824 easy,nonn
%O A052824 0,3
%A A052824 encyclopedia(AT)pommard.inria.fr, Jan 25 2000