[Math] the next row of this pattern

pattern recognition

I'm attempting to help my little sister with her Algebra 1 homework, and this problem showed up. I can't for the life of me figure out the pattern; I was hoping someone would be able to. Here's the given pattern:

1
1 1
2 1
1 1 1 2
3 1 1 2
2 1 1 2 1 3

Thanks!

Best Answer

This is a variation on the look and say sequence, it works as follows: Given the sequence $1231$ it has $2$ ones $1$ two and $1$ three. So the next line would be $211213$. The digits are said from smallest to largest (so we always start saying the number of appearances of digit 1)

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