
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 the sequence $\{a_n\}$, $a_1=1$, $a_{n+1}=(1+ \dfrac {1}{n})a_n+(n+1)\cdot 2^n$.  
(I) Let $b_n= \dfrac {a_n}{n}$, find the general formula for the sequence $\{b_n\}$.  
(II) Find the sum of the first $n$ terms of the sequence $\{a_n\}$, $S_n$.

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