共50条信息
已知正项等比数列\(\left\{ {{a}_{n}} \right\}\)的前\(n\)项和为\({{S}_{n}}\),且\({{a}_{1}}{{a}_{6}}=2{{a}_{3}}\),\({{a}_{4}}\)与\({{a}_{6}}\)的等差中项为\(5\),则\({{S}_{5}}=\)( )
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\(n= (\) \()\)
南北朝时期的数学古籍\(《\)张邱建算经\(》\)有如下一道题:“今有十等人,每等一人,宫赐金以等次差\((\)即等差\()\)降之,上三人,得金四斤,持出;下四人后入得三斤,持出;中间三人未到者,亦依等次更给\(.\)问:每等人比下等人多得几斤?”( )
已知等差数列\(\left\{ {{a}_{n}} \right\}\)的前\(n\)项和\({{S}_{n}}\),满足\({{S}_{3}}=0,{{S}_{5}}=-5\),则数列\(\left\{ \dfrac{1}{{{a}_{2n-1}}{{a}_{2n+1}}} \right\}\)的前\(50\)项和\({{T}_{50}}=\) __________.
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