CREATE TABLE "table1_21025437_3" (
  "episode_no" real,
  "series_no" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "viewers_millions" text,
  "original_airdate" text
);

Question: what is the lowest value under the column series no.?
SQL: SELECT MIN("series_no") FROM "table1_21025437_3";