Another Math question :P

Well, since you all seem to be in the mood to do math; why not try this question? ;)

1
1 1
2 1
1 2 1 1
1 1 1 2 2 1
3 1 2 2 1 1
1 3 1 1 2 2 2 1
1 1 1 3 2 1 3 2 1 1
??????????????????????????

the question is:
What line of numbers comes next???