How many original air dates were there for episode 17?
CREATE TABLE "table1_15430813_1" (
  "no_in_season" real,
  "no_disc" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text
);
SELECT COUNT("original_air_date") FROM "table1_15430813_1" WHERE "no_in_season"=17;