牛人速进2已知Sn是{An}前N项和且有Sn=2An-1 则数列通项An=?

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牛人速进2
已知Sn是{An}前N项和且有Sn=2An-1 则数列通项An=?

A1 = S1 = 2A1 - 1
A1 = 1
An = Sn - S(n-1) = 2An-1 - 2[A(n-1))-1] = 2An -2A(n-1)
An = 2A(n-1)
An = 2^(n-1)

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牛人速进2已知Sn是{An}前N项和 且有Sn=2An-1 则数列通项An=?