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%I #10 Dec 03 2015 10:03:15
%S 1,72,2400,52576,870732,11739984,134825216,1359259200,12290396058,
%T 101268020984,769721861376,5449376818656,36216000728200,
%U 227395735413552,1356190070338560,7717657198319936,42069113073665703,220400042813587800
%N Expansion of ((theta_2)^4+(theta_3)^4)/(Delta_24)^2.
%D J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 105.
%t s = (EllipticTheta[2, 0, q]^4 + EllipticTheta[3, 0, q]^4)/QPochhammer[q]^48 + O[q]^20; CoefficientList[s, q] (* _Jean-François Alcover_, Dec 03 2015 *)
%o (PARI) {a(n)=local(A); if(n<0, 0, A=x*O(x^n); polcoeff( sum(k=1,n, 24*sumdiv(k,d,d%2*d)*x^k, 1+A)/eta(x+A)^48, n))} /* _Michael Somos_, Feb 15 2006 */
%K nonn
%O 0,2
%A _N. J. A. Sloane_
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