8.
已知数列\(\{a_{n}\}\)的前\(n\)项和\(s_{n}\),点\((n,s_{n})(n∈N^{*})\)在函数\(y= \dfrac {1}{2}x^{2}+ \dfrac {1}{2}x\)的图象上
\((1)\)求\(\{a_{n}\}\)的通项公式;
\((2)\)设数列\(\{ \dfrac {1}{a_{n}a_{n+2}}\}\)的前\(n\)项和为\(T_{n}\),不等式\(T_{n} > \dfrac {1}{3}\log _{a}(1-a)\)对任意的正整数恒成立,求实数\(a\)的取值范围.