已知:an=(n=1,2,3,…),记b1=2(1-a1),b2=2(1-a1)(1-a2),…

已知:ann123,…),记b12(1a1)b22(1a1)(1a2),…,

bn2(1a1)(1a2)(1an),则通过计算推测出bn 的表达式bn            .

(用含n的代数式表示).

答案

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