The four numbers in front of a series of numbers are 3, 8, 15, 24..., what is the 10th number?
一组数列前面的四个数字为3、8、15、24…，则第10个数字是多少．
<gadget id="calculator">24 + 11</gadget>
<output>35</output>

<gadget id="calculator">35 + 13</gadget>
<output>48</output>

<gadget id="calculator">48 + 15</gadget>
<output>63</output>

<gadget id="calculator">63 + 17</gadget>
<output>80</output>

<gadget id="calculator">80 + 19</gadget>
<output>99</output>

<gadget id="calculator">99 + 21</gadget>
<output>120</output>

<result>120</result>