Who wrote the episode that aired on April 17, 2011? 
CREATE TABLE "table1_11111116_6" (
  "no_in_season" real,
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_million" text
);
SELECT "written_by" FROM "table1_11111116_6" WHERE "original_air_date"='April 17, 2011';