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_18424435_4 (_number VARCHAR, production_code VARCHAR)
### Question:
What is the total number of episodes listed with a production code of 306?
### Answer:
SELECT COUNT(_number) FROM table_18424435_4 WHERE production_code = 306