
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
A sequence ${a_n}$ consists of 6 terms, among which three terms are 1, two terms are 2, and one term is 3. How many such sequences satisfying the above conditions are there?

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