  We reconsider the computation of the entanglement entropy of two disjoint
intervals in a (1+1) dimensional conformal field theory by conformal block
expansion of the 4-point correlation function of twist fields. We show that
accurate results may be obtained by taking into account several terms in the
operator product expansion (OPE) of twist fields and by iterating the
Zamolodchikov recursion formula for each conformal block. We perform a detailed
analysis for the Ising conformal field theory and for the free compactified
boson. Each term in the conformal block expansion can be easily analytically
continued and so this approach also provides a good approximation for the von
Neumann entropy.
