科研之友
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摘要
Let T(n) be the full transformation semigroup of a finite set, say X(n) = {1,2, ... ,n}, and for a given full transformation alpha : X(n) -> X(n) let F(alpha) = {x is an element of X(n) : x alpha = x} be its set of fixed points. In this note we obtain and discuss formulae for F(n, r, k) = vertical bar{alpha is an element of T(n) : vertical bar Im alpha| = r boolean AND vertical bar F(alpha)vertical bar = k}vertical bar.
- 出版日期2011-9
- 单位中国石油大学（北京）
