
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
Given a sequence $\{a\_n\}$, its first $n$ terms sum is $S\_n$, and $a\_1=1$, $a_{n+1}= \frac {1}{3}S_{n}$, for $n=1$, $2$, $3$, $...$. Find:
- The values of $a\_2$, $a\_3$, $a\_4$ and the general term formula of the sequence $\{a\_n\}$;
- The value of $a\_2+a\_4+a\_6+...+a_{2n}$.

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