给你个思路,写出n+1满足的式子,两式相减得Sn+1,再由Sn-Sn-1得an,具体的如下
已知数列{an}满足:na1+(n-1)a2……+2an-1+an}=(2/3)n次+(2/3)n-1+……+(2/3)
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