CREATE TABLE table_37242 ("Week" FLOAT, "Date" CLOB, "Opponent" CLOB, "Result" CLOB, "Venue" CLOB, "Attendance" FLOAT)

Opponent of at san francisco 49ers had what lowest week?
SELECT MIN("Week") FROM table_37242 WHERE "Opponent" = 'at san francisco 49ers'
SELECT MIN("Week") FROM "table_37242" WHERE "Opponent" = 'at san francisco 49ers'