Table schema:
CREATE TABLE table_name_1 (production_code VARCHAR, original_air_date VARCHAR, season__number VARCHAR, series__number VARCHAR)

Question: What is the production code of the episode before season 8, with a series number less than 31, and aired on September 21, 1995?
SQL: SELECT production_code FROM table_name_1 WHERE season__number < 8 AND series__number < 31 AND original_air_date = "september 21, 1995"