Database: menu
Question: Please list the page numbers of all the menu pages on which the dish "Chicken gumbo" had appeared.
SQL: SELECT T1.page_number FROM MenuPage AS T1 INNER JOIN MenuItem AS T2 ON T1.id = T2.menu_page_id INNER JOIN Dish AS T3 ON T2.dish_id = T3.id WHERE T3.name = 'Chicken gumbo'