2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/63263We shall give a Counting Formula for the number of Fourier-Mukai partners of a K3 surface and consider three applications.AMS LaTeX, 16 pages; title changed, submitted to the proceedings of "Workshop on Algebraic Structures and Moduli Spaces" (Jul.14-20,2003 at CRM, Montreal)Algebraic Geometry14J28; 11R29; 11A41text