Characterization of Absolute Summability Factors

By (A, B) we denote the set of all sequences λ = (λn) such that Σanλn is summable B, whenever Σan is summable A, where A and B are summability methods. In the present paper we characterize the sets (|N̄, pn|, |N̄, qn|k) and (|N̄, pn|k, |N̄, qn|), 1 ≤ k < ∞, using functional analytic techniques, and also extend some known results.