Title: Mathieu subspaces of codimension less than <i>n</i> of Mat<sub><i>n</i></sub>(<i>K</i>)
Abstract: We classify all Mathieu subspaces of of codimension less than n, under the assumption that or . More precisely, we show that any proper Mathieu subspace of of codimension less than n is a subspace of , if or . On the other hand, we show that every subspace of of codimension less than n in is a Mathieu subspace of , if or .