1, 11, 21, 1211, 111221, 312211, 13112221 what is the next number?

1113213211, it's called the "look-and-say sequence"

1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211

A. 1 one B. 2 ones C. 1 two, 2 ones D. 3 ones, 2 twos, 1 one E. 1 three, 1 one, 2 twos, 2 ones. F. etc etc

The next number in the sequence should be 1113213211.

So, your sequence would go something like this...

1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211

The next four terms in your sequence would be...

31131211131221, 13211311123113112211, 11131221133112132113212221, 3113112221232112111312211312113211

- Marlon Nunez