
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 that the sequence $\{a_n\}$ is an arithmetic sequence and satisfies $\overrightarrow{BA}=a_{3} \overrightarrow{OB}+a_{2015} \overrightarrow{OC}$, if $\overrightarrow{AB}=λ \overrightarrow{AC}(λ∈R)$, and point $O$ is a point outside line $BC$, calculate $a_{1}+a_{2017}$.

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