
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 the sequence $\{a_n\}$ is an arithmetic sequence, and $S_n$ is the sum of its first $n$ terms. If $a_3=20$ and $2S_3=S_4+8$,  
(1) Find the general formula for the sequence $\{a_n\}$;  
(2) Let $b_n= \frac {1}{S_n-1}$ ($n\in\mathbb{N}^*$), $T_n=b_1+b_2+\ldots+b_n$, find $T_n$.

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