排列及反序数

Arrangement and Inverse Order

研究n个互异数码排列的反序数的取值范围,确定反序数为k的排列个数的取值范围,并讨论了可重复数码排列的情况.

Examine the range of the inverse order of different numerals'arrangement, give the range of the number of all arrangernents with inverse order k, and discuss the rondition of repeated arrangement.