What is the next number?

Question

This is an easy number puzzle:

1) 1
2) 11
3) 21
4) 1211
5) 111221
6) 312211
7) 13112221
8) ???

What is the number on row 8?

Eh, this one was a little hard to find its dupe, so no biggie. — JonTheMon, Mar 19 '15 at 18:25

Marco Bonelli · Accepted Answer · 2015-03-19T20:49:22.300

1

It is:

1113213211

Explanation:

Each number, from the second line onwards, represents the frequencies of the digits in the previous line in the form $Af_ABf_BCf_C...$, where $A$, $B$ and $C$ are the different digits in order of appearence, and $f_{A,B,C}$ represents their frequency in every continuous set of equal digits.

1
11      one one
21      two ones
1211    one two and one one
111221  one one, one two, and two ones
...

edited Mar 19 '15 at 20:49

answered Mar 19 '15 at 17:15

Marco Bonelli

2,565
2
18
28

Correct guess but careless answer~ – Alex Mar 19 '15 at 17:19
@Alex I edited my answer adding a more precise explaination – Marco Bonelli Mar 19 '15 at 17:32

What is the next number?

1 Answers1

It is:

Explanation:

Linked