Köchel catalogue Köchel catalogue The Köchel catalogue () is a chronological catalogue of compositions by Wolfgang Amadeus Mozart, originally created by Ludwig von Köchel, in which the entries are abbreviated "K." and "KV". The numbers of the Köchel catalogue reflect the continuing establishment of a complete chronology of Mozart's works, and provide a shorthand reference to the compositions. According to Köchel's counting, "Requiem in D minor" is the 626th piece Mozart composed, thus is designated either "K. 626" or "KV 626"; however, his original catalogue (1862) of Mozart has been twice revised, and some works have had three KV. numbers, e.g. Mozart's
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