1
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What is the next number in the following set ?

$$1,11,21,1211,111221, \ldots$$

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closed as primarily opinion-based by Dan Rust, Yiorgos S. Smyrlis, egreg, Nick Peterson, vonbrand Mar 17 '14 at 22:45

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

5
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The next number is 312211. Hint read the sequence out loud!;)

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7
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See the Look-and-Say Sequence.

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3
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$312211$. And since we need $30$ characters...

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