[2014·河北質(zhì)檢]已知數(shù)列{a
n}滿足a
1=5,a
na
n+1=2
n,則
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=( )
A.2 | B.4 | C.5 | D. |
依題意得
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=
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=2,即
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=2,故數(shù)列a
1,a
3,a
5,a
7,…是一個以5為首項、2為公比的等比數(shù)列,因此
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=4,選B.
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