During the last few years of his life, John Cage wrote many pieces in the same general vein as Five3. They are often referred to as "the number pieces." This references the titles of the pieces, which are all simply the number of the performers. Superscripts are added as necessary to distinguish the individual pieces (this is the third quintet, for example).
These works are also called "the time-bracket pieces," a reference to the notation of the pieces.