The function doubles every first character of two consecutive characters in the input string while skipping the second character.

[CODE]:
```python
def approximate_function(input_string):
    output = ""
    for i in range(0, len(input_string), 2):
        output += input_string[i] * 2
    return output
```

Let's do some more testing to check if this approximation holds true.

COMMAND: PYTHON(./temp/function.py "artist" "computer" "robotics")