CREATE TABLE table_16879 ("No. in series" CLOB, "No. in season" CLOB, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Featured character ( s ) " CLOB, "Original air date" CLOB, "U.S. viewers  ( million ) " CLOB)

What are the episode numbers where the episode features Jack & Locke?
SELECT "No. in series" FROM table_16879 WHERE "Featured character(s)" = 'Jack & Locke'
SELECT "No. in series" FROM "table_16879" WHERE "Featured character(s)" = 'Jack & Locke'