who are the writers of the episode whose production code is 176206? 
CREATE TABLE "table1_2866509_1" (
  "no" real,
  "num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "u_s_air_date" text,
  "production_code" real,
  "u_s_viewers_million" text
);
SELECT "written_by" FROM "table1_2866509_1" WHERE "production_code"=176206;