Abstract
In this paper we consider the series with respect to multiplicative systems Σk=1∞ bkxk(x) with non-negative coefficients tending to zero, quasi-monotone coefficients and coefficients of class R0+BV S.It is shown, that there exists the sum f (x) for such series on [0, 1]. We study the problem of integrability of weighted sums of the series. Sufficient conditions to weighted function φ(x) for which φ(x) f (x) ∈ L[0, 1) and φ(x) f (x) ∈ Lp[0, 1), 1 < p < ∞ are found.