Sure, I can help you write a test case generator for the "Sum of Decimal Digits" problem. Below is the implementation of the generator:

```python
import random

def tcgen():
    datasets = []
    num_datasets = random.randint(1, 100)
    
    for _ in range(num_datasets):
        a = random.randint(1, 1000)
        b = random.randint(1, 10000)
        n = random.randint(1, 100)
        datasets.append((a, b, n))
    
    return datasets

def print_test_cases(datasets):
    for a, b, n in datasets:
        print(f"{a} {b} {n}")

# Generate and print test cases
datasets = tcgen()
print_test_cases(datasets)
```

### Explanation of the Test Case Generator:

1. **`tcgen()` Function**:
   - Generates a random number of datasets (between 1 and 100).
   - For each dataset, it randomly selects values for `a` (1 to 1000), `b` (1 to 10000), and `n` (1 to 100).
   - Stores each dataset as a tuple `(a, b, n)` in a list `datasets`.
   - Returns the list `datasets`.

2. **`print_test_cases()` Function**:
   - Accepts the list of datasets.
   - Prints each dataset in the required format.

3. **Usage**:
   - The function `tcgen()` is called to generate random datasets.
   - The `print_test_cases()` function is called with the generated datasets to print them in the required format.

You can run this script to generate a random set of test cases for the "Sum of Decimal Digits" problem. Each time you run it, you will get a different set of test cases.