
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 $\{a_n\}$ is a geometric sequence with $a_1=3$ and $a_4=24$, and the sequence $\{a_n + b_n\}$ is an arithmetic sequence with the first term 4 and common difference 1.

(Ⅰ) Find the general formula for the sequences $\{a_n\}$ and $\{b_n\}$.  
(Ⅱ) 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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