10.
求下列数列的一个通项公式:
\((1)3\),\(5\),\(9\),\(17\),\(33\),\(...\),
\((2)1,0,- \dfrac{1}{3},0, \dfrac{1}{5},0,- \dfrac{1}{7},0,..., \)
\((3) \dfrac{2}{3}, \dfrac{4}{15}, \dfrac{6}{35}, \dfrac{8}{63}, \dfrac{10}{,99},..., \)
\((4)1\),\(3\),\(6\),\(10\),\(15\),\(21\),\(...\),