The league of 400 (21) has what years listed?
CREATE TABLE "most_appearances" (
  "name" text,
  "years" text,
  "league" text,
  "fa_cup" text,
  "league_cup" text,
  "europe" text,
  "other_c" text,
  "total" text
);
SELECT "years" FROM "most_appearances" WHERE "league"='400 (21)';