It’s the Friday Puzzle!


Here is a series of numbers, starting with the number zero.  What is the hidden logic in the series and why can’t it be continued?

0, 1,  8,  10,  19,  90

As ever, please do NOT post your answers, but do say whether you think you have solved it and how long it took.  Solution on Monday.

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.


61 comments on “It’s the Friday Puzzle!

  1. Roland says:

    It can be continued… However most people don’t know the number to continue it…

    • Neil2Russell says:

      Thanks – realised the number you were hinting at and then got the solution.

    • Engywuck says:

      I think I know what you are proposing but that’s not a number 😉

    • Analmouse Coward says:

      There are two numbers which can continue this sequence.

      we are talking astronomical and microscopic though.

    • Nohj says:

      A unit of information is not a number 🙂

    • Julia says:

      I am looking forward to Monday. I looked through all the numbers on Wikipedia, and I still can’t find one that fits.

  2. igeek1 says:

    Got it in a few seconds, surprisingly. Usually not too good at this type. Roland, I couldn’t find a number that matches the criteria you’re hinting at.

  3. Scott says:

    As the tree said to the lumberjack, I’m stumped!

  4. Anonymous says:

    I think I’ve got it, but im not really sure…

  5. Ian R. says:

    Got it, but took about 2 minutes. Spent a long time pondering that gap of 71 at the end, which I guess is what the puzzle creator is hoping will happen.

  6. Had a good puzzle over it for a few minutes but got there. I’m not sure of the alleged continuation number referred to, unless we’re talking of a very small number.

  7. Paul Durrant says:

    About thirty seconds, I just needed to work out what it wasn’t.

  8. Gareth says:

    Took me about 10 seconds. I usually get stumped on these questions, but the answer to that one just jumped out at me.

  9. Mike says:

    Is it the old phone number for SwapShop

  10. Ozzy says:

    Within a minute.

  11. mittfh says:

    I’m stumped. It doesn’t appear to be mathematical (otherwise the series could continue), related to the number of letters / words in the question, Roman numerals, related to days of the week / months of the year, or even in an obscure base.

  12. Shecky R. says:

    about 30 secs. (much quicker than usual for me)

  13. Anonymous says:

    It can be continued….one more very large number

  14. I was in disadvantage once more, but this time I got it – around 2 minutes.

  15. Edgar says:

    Some hours of discontinued thinking 😀

  16. Guest says:

    If unit prefixes count as numbers, then it can be extended, otherwise it cannot be.

  17. sjames1958 says:

    For once I got it quickly – “use the force, Luke”.

  18. alain says:

    Took me at least 5 minutes.
    Damn, those puzzles can be tough for people whose mother tongue is not english.

  19. SeleneBlueSky7 says:

    I think I got it. Less than a minute. 🙂 Nice one.

  20. Paul Tyler says:

    Got it – not sure what the continuation would be though?

  21. MarKill says:

    funny I did have it but then was confused by the comments that it could be continued!

  22. Rob says:

    Got it. About 2 minutes.

  23. Got it. 3 minutes. The leap from 1 to 8 is pretty unusual.

    • Eddie says:

      Surely not more unusual than the leap from 19 to 90…

    • agata says:

      I agree with Thomas.

    • Julia says:

      It is more unusual than the leap from 19 to 90 but no more unusual than the leap from 0 to 1.

    • JohnF says:

      If you consider that there are actually two “rules” at play here for getting the next number in the sequence and apply both of them, then the leap from 1 to 8 (and, equally, from 19 to 90) is the only way it can be.

  24. Toon says:

    about 10-20 seconds.

  25. agata says:

    I think Richard finally taught me how to solve these puzzles 🙂
    I got it with the first idea I had to solve it. So less than a minute. Luckily I wasn’t thinking in Spanish!

  26. Katie says:

    Got it! For the first time ever it took me under a minute, I’m usually pretty awful with puzzles.

  27. Hassan Selim says:

    Well, it only makes sense to me if you remove the zero at the beginning, that’s why I don’t think I got it :\

  28. Hassan Selim says:

    Ok, I got it now 😀 and I know why it can’t be continued 🙂
    Alain’s comment was very helpful 😀

    at first I though it was a date, 19 October 1990, but it turns out that it’s not 🙂
    (I’m allowed to say what is NOT the answer, right?)

  29. Zach says:

    2 seconds. using Google, that is.

    • Anonymous says:

      Exactly. Try coming up with puzzles that haven’t already been solved there, Richard!

  30. Henry Ruddle says:

    Yes, Alain’s comment was useful. Like others I struggled with many possible systems until I realized why that comment was helpful. I’ll be curious to know what very large or microscopic numbers people think come next.

  31. AMWhy says:

    I’m guessing this is specific and science based as I’m stumped.
    I prefer puzzles where you can work out the answer rather than needing specific background knowledge.

  32. Mark says:

    Finally got it! Very good. First looked at it when it was posted, couldn’t work it out, pondered it while at work, looked at it again when I got home. Still no idea. Looked at it again this morning and got it straight away. I guess I needed to sleep on it.

  33. Chris lilley says:

    Solved it in about 4 minutes and hoping it will help with my insomnia.

  34. Nafisa Miyajiwala says:

    15 seconds

  35. erica says:

    big question is, how would the series look in latin?

  36. Eivind Teig says:

    4-5 minuttes, Alain´s comment helped but the other comments helped me to continue the list forever (but it realy cant since it is not a real number as Nohj said! =)

  37. Anonymous says:

    If instead of going from 8 to 10 we went from 8 to 2, then we’d get stuck in an infinite loop: 0182182182…

  38. bill says:

    Ohhhhhhhhh i finally got it – so simple – why do i always think mathematically?!

  39. Caspar says:

    I asked Richard for the answer at EMC…and he LIED(At least it doesn’t coincide with my answer)! Well wouldn’t have been any fun if he jut told us^^

  40. Louis says:

    It was on my mind for over a day, then after 2 minutes with a pen and some paper I get it.

  41. Jerry says:

    Mulled it over in my mind for a while then got it. Looking over the comments, particularly from Alain, Agata, and Hassan Selim, I am convinced I am right.

  42. Jerry says:

    Guest (July 8, 2011) has an interesting take on this as well. And yadda, yadda, yadda.

  43. Juan AR says:

    I got it!! 🙂

  44. Anonymous says:

    In Italian, if the rule is enforced strictly: 0, 8, 80 stop
    If the rule is enforced loosely (meaning I can skip and look for the next best fit): 0, 8, 88, 800, 808, 888, 8800, 8808, 8888, 80008… and it does not end.

  45. Anonymous says:

    By the same token, a loose implementation of the rule could stretch the Latin sequence to 1, 7, 1000, stop (I reckon)

  46. my answer u use the number 8 19 to get a clue. . . . . in my solution the answer is correct i saw your question in 20 minutes and i know the answer…..

  47. that is a illution number i know Bcz the is not a perfect number to answer that question lol hahhaha

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