TITLE: Formula to this pattern? $1$, $11$, $21$, $1211$, $111221$, $\ldots$
QUESTION [6 upvotes]: I have this pattern:
1
11
21
1211
111221

I'm guessing it's a fibo pattern, been at it for hours now. Anyone know?

REPLY [16 votes]: It's known as the look-and-say sequence.

REPLY [2 votes]: In the first row, there is one 1 (11). In the second, two 1s (21). In the third, there is one 2 then one 1 (1211). In the fourth, there is one 1 then one 2 then two 1s (111221). It continues in this way, so the next row would be 312211.