text: Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
  ### Context:
  CREATE TABLE table_name_34 (us__2013_ VARCHAR)
  ### Question:
  What was the U.S birthstone in the 15th-20th century when in 2013 it was amethyst?
  ### Answer:
  SELECT 15 AS th__20th_century FROM table_name_34 WHERE us__2013_ = "amethyst"