12. (6 points) Between the numbers 1 and 2, the first time write 3, to get 13. The second time, write 4 and 5 between 1 and 3, and between 3 and 2, respectively, to get 1435. Thereafter, each time, write the sum of two adjacent numbers between every pair of adjacent numbers already written. This process is repeated a total of 6 times. What is the sum of all the numbers? $\qquad$
【Solution】Solution: 3 is in the middle, with arithmetic sequences on both sides, denoted as $a_{n}, b_{n}$,
with a common difference of $3, a_{1}=1, b_{1}=2$,
$$
a_{8}=1+7 \times 3=22, \quad b_{8}=2+7 \times 3=23 \text {, }
$$

The sum of all numbers:
$$
\begin{array}{l}
8 \times(1+22) \div 2+8 \times(1+23) \div 2+3, \\
=184 \div 2+192 \div 2+3, \\
=92+96+3, \\
=191
\end{array}
$$

Therefore, the answer is: 191 .