%I A028572
%S A028572 1,0,0,4,2,0,0,0,2,0,0,4,4,0,0,0,2,0,0,4,0,0,0,0,4,0,0,8,0,0,0,0,2,0,0,
%T A028572 0,6,0,0,0,0,0,0,4,4,0,0,0,4,0,0,8,0,0,0,0,0,0,0,4,0,0,0,0,2,0,0,4,4,0,
%U A028572 0,0,6,0,0,4,4,0,0,0,0,0,0,4,0,0,0,0,4,0,0,0,0,0,0,0,4,0,0,12,2,0,0,0,
               0
%N A028572 Expansion of theta_3(z)*theta_3(2z)+theta_2(z)*theta_2(2z) in powers 
               of q^(1/4).
%F A028572 Expansion of phi(q^4)*phi(q^8) +4*q^3*psi(q^8)*psi(q^16) in powers of 
               q where phi(),psi() are Ramanujan theta functions.
%F A028572 G.f.: Sum_{n,m} x^(3*(n^2+m^2)+2*n*m) . - Michael Somos Nov 20 2006 */
%e A028572 1 + 4*q^(3/4) +2*q +2*q^2 +4*q^(11/4) +4*q^3 +2*q^4 + 4*q^(19/4) +4*q^6 
               + ...
%o A028572 (PARI) {a(n)=if(n<1, n==0, qfrep([3, 1; 1, 3], n)[n]*2)} /* Michael Somos 
               Nov 20 2006 */
%Y A028572 Sequence in context: A036115 A056582 A105087 this_sequence A107492 A159257 
               A107088
%Y A028572 Adjacent sequences: A028569 A028570 A028571 this_sequence A028573 A028574 
               A028575
%K A028572 nonn
%O A028572 0,4
%A A028572 N. J. A. Sloane (njas(AT)research.att.com).