Question: how many binary numbers can be created by no more than 4 digits
[{'answer': '16', 'provenance': [{'wikipedia_id': '520346', 'title': '4-bit', 'start_paragraph_id': 2, 'start_character': 344, 'end_paragraph_id': 2, 'end_character': 346, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '520346', 'title': '4-bit', 'start_paragraph_id': 13, 'start_character': 0, 'end_paragraph_id': 13, 'end_character': 261, 'bleu_score': 0.9134686294057901, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7908960970681771822}, 'section': 'Section::::Details.\n'}]}]