Klaus' Number Puzzle Answer

And the next two lines are:


1
11
21
1211
111221
312211
13112221

Why, you ask? Each line describes the one before it. The first line is the number one, the second line describes the first: one (number) one. The third line describes the second: two (number) ones. The fourth line describes the third: one (number) two, one (number) one. And so on. Clever, no?