
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
Deﬁne the sequence of positive integers  $a_n$  recursively by  $a_1=7$  and  $a_n=7^{a_{n-1}}$  for all  $n\geq 2$ .  Determine the last two digits of  $a_{2007}$ .

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