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_27 ( week INTEGER, result VARCHAR, opponent VARCHAR )

### Question ###
Which Week has a Result of l 13-16 and an Opponent of at buffalo bills?

### Accurate SQL ###

SELECT AVG(week) FROM table_name_27 WHERE result = "l 13-16" AND opponent = "at buffalo bills"