高考和竞赛中的排列组合问题往往立意新颖、构思精巧,解法灵活,能较好的考查学生分析问题和解决问题的能力倍受命题者的青睐.笔者发现有些排列组合问题,它们和数列知识有着紧密的联系,通过挖掘题目中的隐含条件,建立递推关系,借助化归思想解题,具有很强的可操作性,值得大家尝试. The permutations and combinations in the college entrance examination and competition are often innovative, well-conceived, flexible, and able to better examine students’ ability to analyze and solve problems. They are favored by propositioners. The author finds that there are some permutations and combinations, and they have a series of knowledge. The close connection, through mining the implied condition in the title, establish the recursive relation, solve the problem with the help of the return to the subject, have a very strong operability, it is worth trying.