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A partition is finitary if all its members are finite. For a set , denotes the set of all finitary partitions of . It is shown consistent with (without the axiom of choice) that there exist an infinite set and a surjection from onto . On the other hand, we prove in some theorems concerning for infinite sets , among which are the following: (1) If there is a finitary partition of without singleton blocks, then there are no surjections from onto and no finite-to-one functions from to . (2) For all , . (3) , where is the set of all finite sequences of elements of .

生成讲解博客的中文版本

生成AI智能校验的中文版本