%I A052823
%S A052823 0,0,1,2,4,6,12,18,34,58,106,186,350,630,1180,2190,4114,7710,14600,
%T A052823 27594,52486
%N A052823 A simple grammar: cycles of pairs of sequences.
%H A052823 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=788">
               Encyclopedia of Combinatorial Structures 788</a>
%F A052823 G.f.: Sum(numtheory[phi](j[1])/j[1]*ln(-(x^j[1]-1)^2/(2*x^j[1]-1)), j[1]=1 
               .. infinity)
%p A052823 spec := [S,{B=Sequence(Z,1 <= card),C=Prod(B,B),S= Cycle(C)},unlabeled]: 
               seq(combstruct[count](spec, size=n), n=0..20);
%Y A052823 A000031 - 2.
%Y A052823 Sequence in context: A167777 A007436 A052847 this_sequence A063516 A104352 
               A133488
%Y A052823 Adjacent sequences: A052820 A052821 A052822 this_sequence A052824 A052825 
               A052826
%K A052823 easy,nonn
%O A052823 0,4
%A A052823 encyclopedia(AT)pommard.inria.fr, Jan 25 2000