
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
The sequence $\left\{a_{n}\right\}$ satisfies $a_{1} = 1$, and for each $n \in \mathbf{N}^{*}$, $a_{n}$ and $a_{n+1}$ are the roots of the equation $x^{2} + 3n x + b_{n} = 0$. Find $\sum_{k=1}^{20} b_{k}$.

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