PUZZLEVILLA

This is a recursively defined sequence of numbers which is commonly called as Look and say sequence.

The sequence can be defined as:

# Take a decimal number
# Look at the number, group consecutive runs of the same digit.
# Say the number, from left to right, group by group; as how many of that digit there are - followed by the digit grouped.
# This becomes the next number of the sequence.

3, 13, 1113, 3113, 132113, 1113122113, 311311222113, ?

3 = one three
13 = one one, one three
1113 = three one, one three
3113 = one three, two one, one three
132113 = one one, one three, one two, two one, one three
1113122113 = three one, one three, one one,two two, two one, one three
311311222113 = one three, two one, one three, two one, three two, two one, one three 13211321322113

So the next number in this look and say sequence is 13211321322113