1.
设正项等比数列\(\{a_{n}\}\),\(a_{4}=81\),且\(a_{2}\),\(a_{3}\)的等差中项为\( \dfrac {3}{2}(a_{1}+a_{2})\).
\((I)\)求数列\(\{a_{n}\}\)的通项公式;
\((II)\)若\(b_{n}=\log _{3}a_{2n-1}\),数列\(\{b_{n}\}\)的前\(n\)项和为\(S_{n}\),数列\(\{c_{n}\}{满足}c_{n}= \dfrac {1}{4S_{n}-1}\),\(T_{n}\)为数列\(\{c_{n}\}\)的前\(n\)项和,若\(T_{n} < λn\)恒成立,求\(λ\)的取值范围.