
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
The sequence $\{a_n\}$ is a geometric sequence and $a_n > 0$, $a_1= \frac {1}{2}$, the sum of the first $n$ terms is $S_n$, $S_3+a_3$, $S_5+a_5$, $S_4+a_4$ form an arithmetic sequence.  
(I) Find the general formula of the sequence $\{a_n\}$.  
(II) Find the sum of the first $n$ terms of the sequence $\{na_n\}$, denoted as $T_n$.

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