已知数列\(\{a _{n} \}\)的前\(n\)项和为\(S _{n}\)，且满足\(S _{n} =2a _{n} -1(n∈N ^{*} ).\)
\((1)\)求数列\(\{a _{n} \}\)的通项公式；
\((2)\)求证\( \dfrac {a_{3}}{S_{2}^{2}}+ \dfrac {a_{4}}{S_{3}^{2}}+…+ \dfrac {a_{n+2}}{S_{n+1}^{2}} < 2\)，\(n∈N ^{*}\)．