This is a bit different number sequence. Format and punctuation are on purpose.
What are the blanks?
4
1 2 2
'1 2, 1 1 2 1 1 1 1 2 1 1 1:
1 2 1 1 3, _ _ _ _ _.
Hint 1:
Going down the rabbit hole may lead to a clue.
Also added the knowledge tag. The other odd tag is another hint.