回复：答案

来源: 于 2010-05-02 11:26:07 [旧帖] [给我悄悄话] 本文已被阅读：次

3+3^2+3^3+3^4+...3^n=(3^n-3)/(3-1)=.This result can be getting by induction using combining 3 to 1.The question is that 13 is not included in it.The answer may be not the Max.