已知各项均为正数的等差数列\(\{a_{n}\}\)满足\(a_{4}=2a_{2}\)，且\(a_{1}\)，\(4\)，\(a_{4}\)成等比数列，设\(\{a_{n}\}\)的前\(n\)项和为\(S_{n}\)．

\((1)\)求数列\(\{a_{n}\}\)的通项公式\(;\)

\((2)\)设数列\(\left\{ \dfrac{S_{n}}{n\mathrm{{·}}2^{n}} \right\}\)的前\(n\)项和为\(T_{n}\)，求证：\(T_{n} < 3\)