user: Question: What opponent has an attendance of 20,456?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'September 17, 1950', 'Chicago Bears', 'L 20-24', '21,000']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Attendance" = '20,456';