CREATE TABLE table_21618 ("Series #" FLOAT, "Season #" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT)

Name the series number directed by richard thorpe written by dee johnson
SELECT MAX("Series #") FROM table_21618 WHERE "Directed by" = 'Richard Thorpe' AND "Written by" = 'Dee Johnson'
SELECT MAX("Series #") FROM "table_21618" WHERE "Directed by" = 'Richard Thorpe' AND "Written by" = 'Dee Johnson'