
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
In a non-zero arithmetic sequence $\{{a_n}\}$, if ${a_{n+1} - a_n^2 + a_{n-1} = 0}$ $(n \geqslant 2)$, find the value of ${S_{2n-1} - 4n}$.

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