what is  the series number where the date of first broadcast is 16 october 2008?
CREATE TABLE "table1_12995531_3" (
  "series_number" text,
  "episode_number" real,
  "date_of_first_broadcast" text,
  "total_viewers" real,
  "series_average" real
);
SELECT "series_number" FROM "table1_12995531_3" WHERE "date_of_first_broadcast"='16 October 2008';