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若数列｛ａｎ｝中每一项都含有组合数Ｃｍｎ，则称｛ａｎ｝为组合数列．短文介绍一种利用组合数列的通项求其前ｎ项和的方法．兹举例说明如下：例１求Ｃ１ｎ＋２Ｃ２ｎ＋３Ｃ３ｎ＋…＋ｎＣｎｎ．解所求的和式是以通项ａｋ＝ｋＣｋｎ的组合数列的前ｎ项之和．∵ａｋ＝ｋＣ...
If each item in the series {an} contains a combination number Cmn, {an} is said to be a composite number. The essay introduces a method for finding the sum of the first n terms using the general term of the combination sequence. Here is an example to illustrate: Example 1 find C1n+2C2n+3C3n+...+nCnn. The sum of the solution to the solution is the sum of the first n terms of the composite series of the general term ak=kCkn. ∵ak=kC...