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.

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

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

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

There are two numbers which can continue this sequence.

we are talking astronomical and microscopic though.

A unit of information is not a number 🙂

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

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.

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

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

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.

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.

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

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

Is it the old phone number for SwapShop

Didn’t that begin with an ‘oh’ ?

Within a minute.

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.

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

It can be continued….one more very large number

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

Some hours of discontinued thinking 😀

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

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

Took me at least 5 minutes.

Damn, those puzzles can be tough for people whose mother tongue is not english.

Steady on there, Alain!

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

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

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

Got it. About 2 minutes.

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

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

I agree with Thomas.

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

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.

about 10-20 seconds.

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!

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

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

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?)

2 seconds. using Google, that is.

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

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.

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.

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.

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

15 seconds

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

0.

well the romans didnt have 0 so it would go..

1, 6 then finish

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! =)

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

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

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^^

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

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.

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

I got it!! 🙂

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.

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

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…..

that is a illution number i know Bcz the 0.1.8.19 is not a perfect number to answer that question lol hahhaha