CREATE TABLE table_40640 ("Week" FLOAT, "Date" CLOB, "Opponent" CLOB, "Result" CLOB, "Attendance" CLOB)

Which Week has an Opponent of at seattle seahawks?
SELECT "Week" FROM table_40640 WHERE "Opponent" = 'at seattle seahawks'
SELECT "Week" FROM "table_40640" WHERE "Opponent" = 'at seattle seahawks'