
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 $S_{n}$ is the sum of the first $n$ terms of an arithmetic sequence ${a_{n}}$ with a non-zero common difference, and $a_{1}=1$, $S_{1}$, $S_{2}$, $S_{4}$ form a geometric sequence.
(I) Find the general term formula for the sequence ${a_{n}}$;
(II) Let $b_{n}= \frac {1}{a_{n}a_{n+1}}$, find the sum of the first $n$ terms of the sequence ${b_{n}}$.

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