%I A139631
%S A139631 1,0,1,0,1,1,2,1,2,1,3,2,4,2,5,4,6,5,8,6,11,8,13,10,16,14,20,17,24,21,
%T A139631 31,26,37,32,44,41,54,49,64,59,79,72,94,86,111,106,132,126,156,149,187,
%U A139631 178,219,210,257,251,302,295,352,346,416,406,483,474,560,558,652,648
%N A139631 Expansion of chi(q^5) / chi(-q^2) in powers of q where chi() is a Ramanujan 
               theta function.
%F A139631 Expansion of q^(1/8) * eta(q^4) * eta(q^10)^2 / (eta(q^2) * eta(q^5) 
               * eta(q^20)) in powers of q.
%F A139631 G.f. is a period 1 Fourier series which satisfies f(-1 / (640 t)) = 2^(-1/
               2) g(t) where q = exp(2 pi i t) and g() is g.f. for A139632.
%F A139631 G.f.: Product_{k>0} (1 + x^(2*k)) * (1 + x^(5*k)) / (1 + x^(10*k)).
%e A139631 1/q + q^15 + q^31 + q^39 + 2*q^47 + q^55 + 2*q^63 + q^71 + 3*q^79 + ...
%o A139631 (PARI) {a(n) = local(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^4 
               + A) * eta(x^10 + A)^2 / eta(x^2 + A) / eta(x^5 + A) / eta(x^20 + 
               A), n))}
%Y A139631 A139632(2*n) = a(n).
%Y A139631 Sequence in context: A154958 A025806 A025802 this_sequence A145706 A029177 
               A161229
%Y A139631 Adjacent sequences: A139628 A139629 A139630 this_sequence A139632 A139633 
               A139634
%K A139631 nonn
%O A139631 0,7
%A A139631 Michael Somos, Apr 27 2008