Double sequence spaces extend the classical notion of sequence spaces to encompass two-indexed structures, thereby providing a robust framework for the analysis of functions and operators in ...

Let (un : n = 1, 2, ...) be a sequence of real or complex numbers. We aim in this paper to determine necessary and/or sufficient conditions under which convergence of a sequence (un) or its certain ...

The convergence of diagonal elements of an irreducible symmetric tridiagonal matrix under QL algorithm with some kinds of shift is discussed. It is proved that if α₁—σ→0 and βj→0, j = 1, 2, ···, m, ...