A simple sequence of numbers, which I encountered during intermediate school, in my math book. Any person that finished intermediate school possesses the necessary toolbox required to solve this puzzle. Yet, so far, I have never found anyone that could solve it. I have had many collegues and friends try (and most of them are engineers), but it still remains unsolved.

I have to admit, I didn't solve it either, at the age of 14, but I certainly had the matemathical knowledge to be able to solve it, and the puzzle have been stuck in my mind ever since. It's really great (in my mind).

The start of the sequence is:

8 5 4 9 1 7 6 ...

Considering all the problem solvers here, I assume it will be solved pretty quick :) But it would be fun if it remained unsolved for just a little longer :)


This puzzle is not mathematical at all.


The puzzle is an English-language puzzle

Hint 2:

Think lexicographically! Think alphabetically!


eight, five, four, nine, one, seven, six, three, two, zero --> 8 5 4 9 1 7 6 3 2 0

  • $\begingroup$ Heh, I had the right thought when I saw it. Got stuck at the 9 (four) though, and noticed I was overthinking still. $\endgroup$ – No. 7892142 Jan 30 '15 at 9:33
  • $\begingroup$ I know it was the wrong tag, but I thought it would be too obvious if I picked the "right" tag, so it was intentional to not give away too much information. I must say, I'm rather impressed with how quick the solution came. Although, my original language is Swedish, and thus the original sequence is 1 5 4 9 0 6 7... which usually creates more of a problem (I think) because of the numbers and some relationship between 1 = 5 - 4 and 5 + 4 = 9. $\endgroup$ – RickardNi Jan 30 '15 at 9:59
  • $\begingroup$ sorry, I still dont get it... First I thought it depends on the length of the written numbers (eight=5 letters, five=4 letters) but this is obiously not the solution... $\endgroup$ – MyPasswordIsLasercats Jan 30 '15 at 13:18
  • 2
    $\begingroup$ Essential accompanying film: Fermat's room. $\endgroup$ – user5971 Jan 30 '15 at 14:57
  • 3
    $\begingroup$ @RickardNi: the trouble with using the wrong tag is that it could lead people to think that the solution isn't valid since it doesn't use maths. Fortunately Gerhard answered anyway but may well have thought "No, this can't be right, it uses no maths" and thus didn't answer. You wouldn't (I hope) give incorrect information in any other part of a puzzle. I don't see why the tags should be any different. (and I know that hte question was already retagged long ago but thought I'd give my thinking of why to help in the future). All just opinion though. :) $\endgroup$ – Chris Jan 30 '15 at 16:16

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