3.
设数列\(\{a_{n}\}\)是各项均为正数的等比数列,其前\(n\)项和为\(S_{n}\),若\(a_{1}a_{5}=64\),\(S_{5}-S_{3}=48\).
\((1)\) 求数列\(\{a_{n}\}\)的通项公式\(;\)
\((2)\) 对于正整数\(k\),\(m\),\(l(k < m < l)\),求证:“\(m=k+1\)且\(l=k+3\)”是“\(5a_{k}\),\(a_{m}\),\(a_{l}\)这三项经适当排序后能构成等差数列”的充要条件\(;\)
\((3)\) 设数列\(\{b_{n}\}\)满足:对任意的正整数\(n\),都有\(a_{1}b_{n}+a_{2}b_{n-1}+a_{3}b_{n-2}+…+a_{n}b_{1}=3·2^{n+1}-4n-6\),且集合\(M=\left\{ n\left| \dfrac{b_{n}}{a_{n}}{\geqslant }\lambda\mathrm{{,}}n\mathrm{{∈}}N^{\mathrm{{*}}} \right\} \right.\)中有且仅有\(3\)个元素,试求\(λ\)的取值范围.