There is a set of numbers: 1, 2, 5, 10, 17, 26, ..., please observe the composition rules of this set of numbers, and use the rules you discovered to determine the number eight.
有一组数：1、2、5、10、17、26，…，请观察这组数的构成规律，用你发现的规律确定第8个数为多少．
<gadget id="calculator">7 ** 2</gadget>
<output>49</output>

<gadget id="calculator">49 + 1</gadget>
<output>50</output>

<result>50</result>