Select 7 natural numbers from 1 to 12. It is required that none of the selected numbers is twice as large as another natural number. How many ways are there in total?
从1～12中选出7个自然数，要求选出的数中不存在某个自然数是另一个自然数的2倍，那么一共有多少种选法．
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">3 * 3 * 2</gadget>
<output>18</output>

<gadget id="calculator">3 * 1 * 1</gadget>
<output>3</output>

<gadget id="calculator">3 * 1 * 2 * 3</gadget>
<output>18</output>

<gadget id="calculator">3 + 18</gadget>
<output>21</output>

<gadget id="calculator">8 + 18 + 21</gadget>
<output>47</output>

<result>47</result>