CREATE TABLE table_name_27 (week INT, result VARCHAR, opponent VARCHAR)

Which Week has a Result of l 13-16 and an Opponent of at buffalo bills?
SELECT AVG(week) FROM table_name_27 WHERE result = "l 13-16" AND opponent = "at buffalo bills"
SELECT AVG("week") FROM "table_name_27" WHERE "at buffalo bills" = "opponent" AND "l 13-16" = "result"