共50条信息
已知数列\(\{ a_{n}\}\)满足\(a_{1}{=}1\),\(a_{n}{-}a_{n{-}1}{=}2(n{\geqslant }2)\),则数列的通项\({a}_{n}= \)( )
数列\({a_{n}}\)满足\(a_{1}=1\),\(na_{n+1}=(n+1)a_{n}+n(n+1)\),\(n∈N*\).
\((1)\)证明:数列\(\{\dfrac{{{a}_{n}}}{n}\}\)是等差数列;
\((2)\)设\({{b}_{n}}={{3}^{n}}\sqrt{{{a}_{n}}}\),求数列\({b_{n}}\)的前\(n\)项和\(S_{n}\).
已知数列\(\left\{{a}_{n}\right\} \)中,\({a}_{1}=1,{a}_{2}=4,2{a}_{n}={a}_{n-1}+{a}_{n+1}(n\geqslant 2,n∈{N}^{*}) \) ,当\({a}_{n}=301 \)时,序号\(n= (\) \()\)
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