what is the maximum number in the season wher the us viewers is 2.59?
CREATE TABLE "table1_20726262_4" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directedby" text,
  "writtenby" text,
  "originalairdate" text,
  "production_code" text,
  "u_s_viewers_million" text
);
SELECT MAX("no_in_season") FROM "table1_20726262_4" WHERE "u_s_viewers_million"='2.59';