find the next number in the sequence


think about all of the numbers and the number after it

it is not 311223

you need think outside the box

this is not a math question

  • 3
    $\begingroup$ Does this answer your question? Interview Question or Pathbreaking puzzle (Just the numbers have been rearranged slightly to use a numeric order, but they are essentially the same premise...) $\endgroup$
    – Stiv
    Jul 7, 2020 at 20:42
  • $\begingroup$ OEIS: oeis.org/A005151 Also note that it is a variant of the much better known Look and Say sequence with the digits being counted arranged in ascending order. The Look and Say sequence's general term is based on how the previous term is arranged. OEIS: oeis.org/A005150 $\endgroup$
    – Deepak
    Jul 8, 2020 at 14:14

1 Answer 1


1 has $1$ one, so 11.
11 has $2$ ones, so 21.

You do this until you get

Now, 211213 has $3$ ones, $2$ twos and $1$ three.

So the answer is



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