Question: when was the last time the oakland a's were no hit
[{'answer': 'April 21 , 2018', 'provenance': [{'wikipedia_id': '29742149', 'title': 'List of Oakland Athletics no-hitters', 'start_paragraph_id': 2, 'start_character': 134, 'end_paragraph_id': 2, 'end_character': 149, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]