CREATE TABLE table_532 ("Series #" FLOAT, "Season #" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT)

What is the series number for Season #18?
SELECT MIN("Series #") FROM table_532 WHERE "Season #" = '18'
SELECT MIN("Series #") FROM "table_532" WHERE "Season #" = '18'