Find the number of `n` digit numbers, which contain the digits 2 and 7, but not the digits 0, 1, 8, 9.

Explanation

To solve the problem of finding the number of `n`-digit numbers that contain the digits 2 and 7, but do not contain the digits 0, 1, 8, or 9, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Valid Digits**:
The digits that can be used are 2, 3, 4, 5, 6, and 7. This gives us a total of 6 valid digits.

2. **Total `n`-Digit Numbers**:
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