column of numbers arranged according to a certain rule is: 3, (5/3), (9/5), (17/7), (33/9), (65/11)...According to this rule, in this column of numbers What is the 9th number in ?
按一定规律排列的一列数依次是：3、(5/3)、(9/5)、(17/7)、(33/9)、(65/11)…照此规律，这列数中的第9个数是多少？
<gadget id="calculator">2 ** 9</gadget>
<output>512</output>

<gadget id="calculator">512 + 1</gadget>
<output>513</output>

<gadget id="calculator">2 * 9</gadget>
<output>18</output>

<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<gadget id="calculator">513 / 17</gadget>
<output>513/17 = around 30.176471</output>

<result>513/17 = around 30.176471</result>