For the first time between the numbers 1 and 2, write 3. For the second time, write 4, 5 between 1, 3 and 3, 2 respectively. Each time, write the sum of these two numbers between two adjacent numbers that have already been written down. This process was repeated seven times. What is the sum of all the numbers at this time?
第一次在1、2两数之间，写上3．第二次在1、3和3、2之间分别写上4、5．每次都在已写下的两个相邻数之间写上这两个数之和．这样的过程共重复了七次．这时所有数的和是多少．
<gadget id="calculator">3 ** 1</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3 ** 3</gadget>
<output>27</output>

<gadget id="calculator">3 ** 4</gadget>
<output>81</output>

<gadget id="calculator">3 ** 5</gadget>
<output>243</output>

<gadget id="calculator">3 ** 6</gadget>
<output>729</output>

<gadget id="calculator">3 ** 7</gadget>
<output>2_187</output>

<gadget id="calculator">1 + 2 + 3 + 9 + 27 + 81 + 243 + 729 + 2_187</gadget>
<output>3_282</output>

<result>3_282</result>