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_30278 ( "Series no." real, "Season no." real, "Title" text, "Directed by" text, "Written by" text, "Original air date" text, "Production code" real, "U.S. viewers (millions)" text )

### Question ###
What season number was assigned to the episode identified with the production code 401?

### Accurate SQL ###

SELECT "Season no." FROM table_30278 WHERE "Production code" = '401'