
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
Let ${s_n}$ be the sum of the first $n$ terms of the sequence ${{a_n}}$, and ${s_n}=\frac{3}{2}\left( {{a_n}}-1 \right)\left( n\in N,n\geqslant 1 \right)$. Determine the expression for $a_n$.

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