CREATE TABLE table_23176 ("Episode #" FLOAT, "Prod #" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Originalairdate" TEXT, "Filmed" TEXT)

What was the production number of the episode filmed in aug/sept 1968?
SELECT "Prod #" FROM table_23176 WHERE "Filmed" = 'Aug/Sept 1968'
SELECT "Prod #" FROM "table_23176" WHERE "Filmed" = 'Aug/Sept 1968'