(1/2), (1/6), (1/12), (1/20)... What is the sum of the first 30 numbers?
(1/2)，(1/6)，(1/12)，(1/20)…前30个数的和为多少．
<gadget id="calculator">1 / 31</gadget>
<output>1/31 = around 0.032258</output>

<gadget id="calculator">1 - (1/31)</gadget>
<output>30/31 = around 0.967742</output>

<result>30/31 = around 0.967742</result>