A series of numbers are arranged according to the rules: 1, 2, 3, 2, 3, 4, 3, 4, 5, 4, 5, 6, ... Counting from the first number, what is the sum of the first 60 numbers.
一串数按规律排列：1，2，3，2，3，4，3，4，5，4，5，6，…从第一个数算起，前60个数的和是多少．
<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<gadget id="calculator">6 * 20</gadget>
<output>120</output>

<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">20 * 19 * (3/2)</gadget>
<output>570</output>

<gadget id="calculator">120 + 570</gadget>
<output>690</output>

<result>690</result>