“…Arora et al in [6] show that a multiplication operator acting on Lorentz sequence spaces is compact if and only if ∈ 0 , that is, if and only if ( ) → 0 as → ∞. This last condition also characterizes the compactness of this operator , acting on other Banach sequence spaces such as Orlicz-Lorentz sequence spaces [10], Cesàro sequence spaces [11], Cesàro-Orlicz sequence spaces [12], among others. However, the above spaces are classified as Köthe sequence spaces and the characterization of compactness (and other properties) of multiplication operators acting on Köthe sequence spaces is due to Ramos-Fernández and Salas-Brown [13] (see also [14,15]).…”