根据题意得1*(1+2d)=(1+d)^2得到1+2d=1+2d+d^2最后d=0,题目要求是递增的即系d>0,矛盾吧,或许我算错了
递增等差数列an满足a1=1,a1,a2,a3为等比数列.设bn=an+2的an次方,求数列bn的前n向和sn
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