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_name_20 (week INTEGER, date VARCHAR, attendance VARCHAR)

### Question ###
What is the sum of the weeks that games occured on october 21, 1974 and less than 50,623 fans attended?

### Accurate SQL ###

SELECT SUM(week) FROM table_name_20 WHERE date = "october 21, 1974" AND attendance < 50 OFFSET 623