
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
15. There are \(m\) people (\(m \geqslant 2\)) passing a ball to each other, such that after receiving the ball, they immediately pass it to someone else. Initially, person A starts with the ball, marking the first pass. Determine the number of ways \(a_n\) in which the ball returns to person A's hands after \(n\) passes.

Present the answer in LaTex format: \boxed{Your answer}
user