%I A093073
%S A093073 1,1,2,1,0,2,1,0,0,1,0,4,1,0,4,0,0,2,1,0,8,2,0,8,0,0,2,2,0,16,3,0,16,1,
%T A093073 0,4,4,0,28,4,0,28,1,0,8,4,0,48,6,0,46,1,0,12,5,0,80,8,0,76,1,0,20,8,0,
%U A093073 126,10,0,120,2,0,32,11,0,196,14,0,184,4,0,48
%V A093073 1,-1,-2,1,0,2,1,0,0,-1,0,-4,-1,0,4,0,0,2,1,0,-8,2,0,8,0,0,2,-2,0,-16,
               -3,0,16,-1,0,4,4,
%W A093073 0,-28,4,0,28,1,0,8,-4,0,-48,-6,0,46,-1,0,12,5,0,-80,8,0,76,1,0,20,-8,
               0,-126,-10,0,120,
%X A093073 -2,0,32,11,0,-196,14,0,184,4,0,48
%N A093073 Expansion of eta(q)*eta(q^2)/(eta(q^9)eta(q^18)) in powers of q.
%C A093073 Euler transform of period 18 sequence [ -1,-2,-1,-2,-1,-2,-1,-2,0,-2,
               -1,-2,-1,-2,-1,-2,-1,...].
%C A093073 G.f. A(x)=y satisfies 0=f(A(x),A(x^2)) where f(u,v)=u^4+v^4 -uv((u+v)^2+9(u+v)+uv(u+v+4)).
%C A093073 a(3n-1)=A062242(n), a(3n+1)=-2*A092848(n). a(3n)=0, if n>0.
%o A093073 (PARI) a(n)=if(n<-1,0,n++; X=x+x*O(x^n); polcoeff(eta(X)*eta(X^2)/eta(X^9)/
               eta(X^18),n))
%Y A093073 Essentially same as A058531.
%Y A093073 Sequence in context: A093201 A067613 A058531 this_sequence A156319 A083650 
               A030204
%Y A093073 Adjacent sequences: A093070 A093071 A093072 this_sequence A093074 A093075 
               A093076
%K A093073 sign
%O A093073 -1,3
%A A093073 Michael Somos, Mar 17 2004