What are the episode numbers where the episode features Jack & Locke?
CREATE TABLE table_16879 (
    "No. in series" text,
    "No. in season" text,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Featured character(s)" text,
    "Original air date" text,
    "U.S. viewers (million)" text
)
SELECT "No. in series" FROM table_16879 WHERE "Featured character(s)" = 'Jack & Locke'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What are the episode numbers where the episode features Jack & Locke? ### Input: CREATE TABLE table_16879 (
    "No. in series" text,
    "No. in season" text,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Featured character(s)" text,
    "Original air date" text,
    "U.S. viewers (million)" text
) ### Response: SELECT "No. in series" FROM table_16879 WHERE "Featured character(s)" = 'Jack & Locke'