%N Theta series of hexagonal net with respect to midpoint of edge.
%D N. J. A. Sloane, Theta series and magic numbers for diamond and certain ionic crystal structures, J. Math. Phys. 28 (1987), 1653-1657.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%p theta2:=x->add(2*x^((2*n-1)^2/4),n=1..200): phi1:=x->theta2(x^(1/4))*theta2(x^(3/4))/2: seq(coeff(convert(series(phi1(x^4)-phi1(x^12),x,200),polynom),x,n),n=0..200); # Herman Jamke (hermanjamke(AT)fastmail.fm), Feb 28 2008
%A _N. J. A. Sloane_
%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Feb 28 2008