Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_2409041_6 ( no_in_series VARCHAR, no_in_season VARCHAR )

### Question ###
In which series was season 18?

### Accurate SQL ###

SELECT COUNT(no_in_series) FROM table_2409041_6 WHERE no_in_season = 18