There is a column of numbers: 2, 5, 8, 11, 14, ... What is the 20th number in this column.
有一列数：2、5、8、11、14、…这列数中第20个数是多少．
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">19 * 3</gadget>
<output>57</output>

<gadget id="calculator">2 + 57</gadget>
<output>59</output>

<result>59</result>