In a number sequence of 1, 11, 21, 1112, 3112, 211213, why is the next number 312213?


marked as duplicate by JonTheMon, Deusovi, Mike Earnest, f'', Will May 11 '16 at 18:28

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  • $\begingroup$ This is a classic question, follow the link above. $\endgroup$ – Block May 11 '16 at 15:37
  • 1
    $\begingroup$ It's not an exact duplicate, but it is a duplicate of a question that was closed as a duplicate of that one. $\endgroup$ – f'' May 11 '16 at 18:22
  • $\begingroup$ Go here at $5$:$33$, youtube.com/watch?v=r5P-f5arPXE $\endgroup$ – user477343 May 4 '18 at 7:08

This looks like

A sorted version of the Look-and-Say sequence

In this version

You sort the digits first, then count left to right. So $211213$ sorted is $111223$ which has
$3$ $1$s,
$2$ $2$s and
$1$ $3$ which gives the next number $312213$


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