20030630, 16:38  #1 
Aug 2002
London, UK
2^{2}×23 Posts 
Continue this series
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! 
20030630, 19:02  #2 
Sep 2002
2^{3}×103 Posts 
I think the next number should be 210.

20030630, 19:07  #3 
Dec 2002
Frederick County, MD
2×5×37 Posts 
How about 98?

20030630, 19:53  #4  
"Richard B. Woods"
Aug 2002
Wisconsin USA
17014_{8} Posts 
Quote:


20030630, 20:19  #5 
Aug 2002
5×1,697 Posts 
I think I got the answer, but I cheated and looked it up so now I feel all guilty...

20030701, 11:54  #6 
Bamboozled!
"๐บ๐๐ท๐ท๐ญ"
May 2003
Down not across
11423_{10} Posts 
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.) 
20030701, 12:04  #7 
Nov 2002
Vienna, Austria
41_{10} Posts 
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 
20030701, 13:41  #8 
Aug 2002
London, UK
2^{2}×23 Posts 
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! ) 
20030701, 15:22  #9 
Nov 2002
Vienna, Austria
41 Posts 
Next try: :idea:
The first two elements are 2 and 4. Every element with an index > 2 is created by adding the element i1 and the factorial of i2, 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) 
20030701, 15:32  #10 
Jun 2003
2^{6} Posts 
What about 2,4,6,30,180,1470,14850,......?

20030702, 13:49  #11 
Aug 2002
London, UK
5C_{16} Posts 
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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