898460640domain: NAppears in sequencesa(n) = Pell(n)*A008655(n) for n>=1, with a(0)=1, where A008655 lists the coefficients in (theta_3(x)*theta_3(3*x)+theta_2(x)*theta_2(3*x))^4.at n=12A209448E.g.f. A(x) satisfies A(x) = 1 + x*A(x)^2 * (exp(x^2*A(x)) - 1).at n=11A392955