CREATE TABLE "table1_22948559_1" (
  "no_in_series" text,
  "no_in_season" text,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_millions" text
);

Question: Name the production code for number in season being 21
SQL: SELECT "production_code" FROM "table1_22948559_1" WHERE "no_in_season"='21';

Question: Name the production code by paul lieberstein
SQL: SELECT "production_code" FROM "table1_22948559_1" WHERE "written_by"='Paul Lieberstein';