A theater has 20 rows of seats, the first row has 38 seats, and each subsequent row has 2 more seats than the previous row. How many seats are there in total in this theater?
一个剧场设置了20排座位，第一排有38个座位，往后每一排都比前一排多2个座位．这个剧场一共设置了多少个座位？
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">19 * 2</gadget>
<output>38</output>

<gadget id="calculator">38 + 38</gadget>
<output>76</output>

<gadget id="calculator">38 + 76</gadget>
<output>114</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">114 * 10</gadget>
<output>1_140</output>

<result>1_140</result>