  Let (a,b) be a finite interval and 1/p, q, r be functions from L1(a,b). We
show that a general solution (in the weak sense) of the equation (pu')'+qu =
zru on (a,b) can be constructed in terms of power series of the spectral
parameter z. The series converge uniformly on [a,b] and the corresponding
coefficients are constructed by means of a simple recursive procedure. We use
this representation to solve different types of eigenvalue problems. Several
numerical tests are discussed.
