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Old 2003-06-30, 16:38   #1
Reboot It
 
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You are welcome to puzzle over this series. Despite the short excerpt shown, it is possible to work out the basis of the series from just these four numbers.

2
4
6
30

What comes next? How is the series constructed? Be warned - it may not be quite what you think!

If you know straightaway, please do not spoil it for others: just post the fact in the thread and either withhold the answer for a couple of days or send me a private message with your answer.

If there are no responses I may add some further numbers later. Enjoy!
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Old 2003-06-30, 19:02   #2
Jwb52z
 
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I think the next number should be 210.
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Old 2003-06-30, 19:07   #3
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How about 98?
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Old 2003-06-30, 19:53   #4
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Quote:
If there are no responses I may add some further numbers later.
Not too soon!
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Old 2003-06-30, 20:19   #5
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I think I got the answer, but I cheated and looked it up so now I feel all guilty...
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Old 2003-07-01, 11:54   #6
xilman
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As the answer to the ultimate question to life, the universe and everything is 42, your series must be the quartic (6 + 70x - 110x^2 + 53x^3 - 7x^4)/3 evaluated at 0, 1, 2, 3, ...


Paul

(The above answer indicates why I loathe questions like this appearing in IQ tests.)
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Old 2003-07-01, 12:04   #7
koal
 
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I agree with eepiccolo: the next number is 98, followed by 232, 454, 786, ...

The Cubic

y = (11x^3 -66x^2 +127x -66) / 3

does this for x = 1, 2, 3, 4, ...

;) 2*7^2
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Old 2003-07-01, 13:41   #8
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Well I'm sorry to disappoint you all, but nobody has yet posted the correct answer in this thread. I have received a number of private messages, but I shan't disclose them here (yet).

I'll leave it another day or so before posting on how the series continues. (Oh I love keeping all these brilliant minds in suspense! )
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Old 2003-07-01, 15:22   #9
koal
 
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Next try: :idea:

The first two elements are 2 and 4. Every element with an index > 2 is created by adding the element i-1 and the factorial of i-2, which gives the sequence:
1) => 2
2) => 4
3) => 6=4+2!
4) => 30=6+4!
5) => 750=30+6!
6) => 265252859812191058636308480000750=750+30!

...

Okkie? 8)
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Old 2003-07-01, 15:32   #10
hyh1048576
 
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What about 2,4,6,30,180,1470,14850,......?
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Old 2003-07-02, 13:49   #11
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Well, I'm quite pleased that this little teaser has generated a little flurry of interest here. I think it is time to tell you a little bit more.

I'm sorry that nobody has yet posted in this thread how the sequence continues, and all of the numbers put forward as putative subsequent members of the series do not actually appear anywhere in the series, with the exception of 42, although it is not the next number in the series but appears later.

Some clues: The solution does not involve a polynomial at all. The series cannot be proved, or even formulated, inductively. Knowing what is not involved should help all you puzzlers still out there.

I will leave it to public demand to see whether you want some further numbers in the series...
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