def steps_recursive(n, steps = None, line = ""):
    """Return a list of "n" progression steps, using recursion."""
    if steps is None:
        steps = []

    if len(steps) == n:
        return steps

    if len(line) == n:
        steps.append(line)
        return steps_recursive(n, steps)

    line += "#" if len(line) <= len(steps) else " "
    return steps_recursive(n, steps, line)