已知数列{an}满足a1=1,Sn=[(n+1)/2]*an,求通项an.急,思路也要

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已知数列{an}满足a1=1,Sn=[(n+1)/2]*an,求通项an.急,思路也要
已知数列{an}满足a1=1,Sn=[(n+1)/2]*an,求通项an.急,思路也要

已知数列{an}满足a1=1,Sn=[(n+1)/2]*an,求通项an.急,思路也要
由题意得an=Sn-S(n-1)这个你知道吧?n-1是Sn下面的
∴an=[(n+1)/2]*an-[(n-1+1)/2]*a(n-1) 这个n-1也是 an下面的
∵d=an-a(n-1)∴an=nd你自己总能化简吧?
然后代∵an=a1+(n-1)d
把an=nd代入得d=1
∴an=1+(n-1)*1

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