Question

在数列{An}中,A1=1,An*An+1=4^n,求前n项和Sn

在数列{An}中,A1=1,An*An+1=4^n,求前n项和Sn
越详细越好．
n为奇数时An=2^n-1
n为偶数时An=2^n
是怎么得到的

Answer 1

An*An+1=4^n 把此试记为一
An-1*An=4^(n-1) 把此试记为二
一二两式左右两边相除得An+1/An-1=4
易得A1=1,A2=4
n为奇数时An=2^n-1
n为偶数时An=2^n
后面，恩，自己算吧.

Answer 2

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Taurus, Libra ... ... Half ugly dinosaur

these signs of Venus in the guardians of beauty, and of the appearance is very importance for body maintenance is sparing no effort, so if people call her Half or ugly,cheap jimmy choo shoes, they will find it fails, then They will be more of the ways to make oneself more beautiful, for others the nickname, and she no longer together.

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Answer 3

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