TeX source:

\begin{array}{lll} a_1 = 3 \\ a_2 = 2a_{1} - 1 = 2(3) - 1 =5 \\ a_3 = 2a_{2} - 1 = 2(5) - 1 =9 \\ a_4 = 2a_{3} - 1 = 2(9) - 1 =17 \\ \end{array}