Let be any integer. A lattice in the complex plane with period ratio has a sublattice with period ratio . The latter lattice is one of a finite set of sublattices permuted by the modular group , which is based on changes of basis for . Let denote the elliptic modular function of Felix Klein. Define the polynomial as the product of the differences over the conjugate sublattices. As a polynomial in , has coefficients that are polynomials over formula_1 in .