CREATE TABLE "table1_25668962_1" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_million" text
);

Question: What episode number in the series was viewed by 13.66 million people in the U.S.?
SQL: SELECT MAX("no_in_series") FROM "table1_25668962_1" WHERE "u_s_viewers_million"='13.66';

Question: How many million U.S. viewers watched the epiode with a production code of 1arc12?
SQL: SELECT "u_s_viewers_million" FROM "table1_25668962_1" WHERE "production_code"='1ARC12';

Question: How many million U.S. viewers watched the episode with a production code of 1arc03?
SQL: SELECT "u_s_viewers_million" FROM "table1_25668962_1" WHERE "production_code"='1ARC03';

Question: How many million U.S. viewers watched episode number 6 in the series?
SQL: SELECT "u_s_viewers_million" FROM "table1_25668962_1" WHERE "no_in_series"=6;

Question: Who directed episode number 18 in the series?
SQL: SELECT "directed_by" FROM "table1_25668962_1" WHERE "no_in_series"=18;