How many episodes have the season number of 1?
CREATE TABLE "table1_17152787_3" (
  "series_num" real,
  "season_num" real,
  "title" text,
  "directed_by" text,
  "original_air_date" text,
  "prod_code" real
);
SELECT COUNT("series_num") FROM "table1_17152787_3" WHERE "season_num"=1;