Four-Letter Words: The Distribution of Pattern Frequencies in Ring Permutations
四字母词:环形排列中模式频数的分布
Summary An alphabet of c letters is considered. There are, then, ck possible ordered sequences of k of these. Such k-sequences are grouped into λ mutually exclusive and exhaustive sets; members of each set (called k-patterns) are counted the same. A general expression for the joint generating function of the frequencies of occurrence of the different k-patterns is obtained when r letters, with fixed numbers of each sort, are randomly arranged in a ring. In particular,…