試題分析:∵
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,∴
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成首項為1公差為2的等差數(shù)列,∴
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,故選A
點評:求解等差數(shù)列的片段和問題常常利用數(shù)列的前n項和的性質(zhì):數(shù)列
Sm,
S2m-
Sm,
S3m-
S2m,…,仍成等差數(shù)列,公差為
m2d.
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數(shù)列
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滿足
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,且

.
(1)求

(2)是否存在實數(shù)t,使得

,且{

}為等差數(shù)列?若存在,求出t的值;若不存在,說明理由.
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
:

,即當

時,記
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.記

. 對于

,定義集合

是

的整數(shù)倍,

,且

.
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
中元素的個數(shù);
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
中元素的個數(shù).
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
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
項和為

,若

,

,則

( )
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已知數(shù)列{

}的前n項和

,數(shù)列{

}滿足

=

.
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
}是等差數(shù)列,并求數(shù)列{

}的通項公式;
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
,數(shù)列{

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
中,

是其前

項和,

,且

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
________,

______;
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