391
421
481
511
Answer is Right!
Answer is Wrong!
The answer is $\boxed{481}$.
The sequence is $a_n = 3^n – 2^n$.
Here is a brief explanation of each option:
- Option A: $391 = 3^2 \cdot 73$. This is not a term in the sequence, because $73$ is not a power of $3$.
- Option B: $421 = 3^2 \cdot 57$. This is not a term in the sequence, because $57$ is not a power of $3$.
- Option C: $481 = 3^4 \cdot 7$. This is a term in the sequence, because $7$ is a power of $3$.
- Option D: $511 = 3^3 \cdot 17$. This is not a term in the sequence, because $17$ is not a power of $3$.