At the end of the factor base, any "A[]" containing a value above a threshold of roughly log("x2-n") will correspond to a value of "y"("x") which splits over the factor base. The information about exactly which primes divide "y"("x") has been lost, but it has only small factors, and there are many good algorithms for factoring a number known to have only small factors, such as trial division by small primes, SQUFOF, Pollard rho, and ECM, which are usually used in some combination.