
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
A sequence of numbers arranged in a specific order is called a series, such as 1, 3, 9, 19, 33, … This is an example of a series. If starting from the second number, each number in the series has a constant difference with the preceding number, then this series is called an arithmetic sequence, and this constant difference is known as the common difference. For example, 2, 4, 6, 8, 10 is an arithmetic sequence with a common difference of 2. If a series generates a new series by taking the difference between consecutive numbers, and this new series is an arithmetic sequence, then the original series is called a second-order arithmetic sequence. For instance, the series 1, 3, 9, 19, 33, ... leads to a new series 2, 6, 10, 14, ... with a common difference of 4. Therefore, the series 1, 3, 9, 19, 33, ... is a second-order arithmetic sequence. What is the fifth number in the second-order arithmetic sequence 1, 3, 7, 13, ...?

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