
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 an arithmetic sequence $\{a_n\}$ where $a_{1} = -1$ and $a_{3} = 3$,
1. Find the formula for $a_n$;
2. Define another sequence $\{b_n\}$ where $b_n = 2^{a_n}$. Determine whether $\{b_n\}$ is an arithmetic or geometric sequence and explain why.

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