7. Arrange the numbers $1,2, \cdots, 6$ in a random sequence to form a series, requiring that the series first increases and then decreases. How many such series are there? $\qquad$个.
7. 30 .

Select one number from $1,2, \cdots, 5$ to place on the right side of 6, and the rest of the numbers on the left side of 6, to get an increasing then decreasing sequence, there are $\mathrm{C}_{5}^{1}$ such sequences;

Select two numbers from $1,2, \cdots, 5$ to place on the right side of 6, and the rest of the numbers on the left side of 6, to get an increasing then decreasing sequence, there are $\mathrm{C}_{5}^{2}$ such sequences; $\qquad$
Therefore, the total number of sequences that meet the condition is
$$
C_{5}^{1}+C_{5}^{2}+C_{5}^{3}+C_{5}^{4}=2^{5}-2=30 .
$$