CREATE TABLE table_57842 ("Week" FLOAT, "Date" TEXT, "Opponent" TEXT, "Result" TEXT, "Attendance" TEXT)

What week number saw a w 31-16 result?
SELECT MIN("Week") FROM table_57842 WHERE "Result" = 'w 31-16'
SELECT MIN("Week") FROM "table_57842" WHERE "Result" = 'w 31-16'