Köchel catalogue son's earlier works; Mozart's catalogue of his own compositions (begun in February 1784 with K. 449) allows relatively precise dating of many of his later works. The catalogue included the opening bars of each piece, known as an incipit. Köchel divided the corpus into a main chronology of 626 works, and five appendices ("" in German, abbreviated to "Anh.") The appendices (Anh. I-V) included: Since Köchel published his original catalogue in 1863 (now referred to as K), the dating of Mozart's compositions has been subject to constant revision. Many more pieces have since been found, re-dated, re-attributed and re-numbered, requiring
Rencontres numbers Rencontres numbers In combinatorial mathematics, the rencontres numbers are a triangular array of integers that enumerate permutations of the set { 1, ..., "n" } with specified numbers of fixed points: in other words, partial derangements. ("Rencontre" is French for "encounter". By some accounts, the problem is named after a solitaire game.) For "n" ≥ 0 and 0 ≤ "k" ≤ "n", the rencontres number "D" is the number of permutations of { 1, ..., "n" } that have exactly "k" fixed points. For example, if seven presents are given to seven different people, but only two are destined to