2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/75738The aim of this paper is to introduce a new notion of sequences called dd-sequences and show that this notion may be convenient for studying the polynomial property of partial Euler-Poincare' characteristics of the Koszul complex with respect to the powers of a system of parameters. Some results about the dd-sequences, the partial Euler-Poincare' characteristics and the lengths of local cohomology modules are presented in the paper. There are also applications of dd-sequences on the structure of sequentially Cohen-Macaulay modules.26 pagesCommutative Algebra13D99, 13D45, 13H15text