Sure, I can help you write a test case generator for the given problem. Here is a Python function that generates test cases for "Problem A: Decimal Sequences":

```python
import random

def generate_test_case():
    # Generate the number of digits, n
    n = random.randint(1, 1000)
    
    # Generate a sequence of n digits (each digit is between 0 and 9)
    digits = [random.randint(0, 9) for _ in range(n)]
    
    return n, digits

def format_test_case(n, digits):
    # Format the test case to match the input format
    test_case = f"{n}\n" + " ".join(map(str, digits))
    return test_case

# Example usage
for _ in range(5):  # Generate 5 example test cases
    n, digits = generate_test_case()
    test_case = format_test_case(n, digits)
    print("Test Case:")
    print(test_case)
    print()
```

### Explanation:

1. **`generate_test_case()`**:
   - It generates a random integer `n` (1 ≤ n ≤ 1000).
   - It creates a list of `n` random digits (each digit is between 0 and 9).

2. **`format_test_case(n, digits)`**:
   - It formats the generated test case to match the input format specified in the problem statement.
   - The formatted test case consists of `n` followed by a newline, and then the `n` digits separated by spaces.

In the **example usage** section, the code generates and prints 5 example test cases. You can adjust the number of test cases by changing the range in the for loop.