If the addition formula arranged according to a certain rule is 3+4, 5+9, 7+14, 9+19, 11+24, ... then what is the 20th formula?
如果按一定规律排出的加法算式是3+4，5+9，7+14，9+19，11+24，…那么第20个算式是多少．
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

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

<gadget id="calculator">3 + 38</gadget>
<output>41</output>

<gadget id="calculator">19 * 5</gadget>
<output>95</output>

<gadget id="calculator">4 + 95</gadget>
<output>99</output>

<gadget id="calculator">41 + 99</gadget>
<output>140</output>

<result>140</result>