4.
设数列\(\{a_{n}\}\)的各项均为正数,前\(n\)项和为\(S_{n}\),对于任意的\(n∈N_{+}\),\(a_{n}\),\(S_{n}\),\(a_{n}^{2}\)成等差数列,设数列\(\{b_{n}\}\)的前\(n\)项和为\(T_{n}\),且\(b_{n}= \dfrac {(\ln x)^{n}}{a_{n}^{2}}\),若对任意的实数\(x∈(1,e](e\)是自然对数的底\()\)和任意正整数\(n\),总有\(T_{n} < r(r∈N_{+})\),则\(r\)的最小值为 ______ .