2, 5, 12, 31, 86....
Series teasers are where you try to complete the sequence of a series of letters, numbers or objects.
What's the next number in this sequence?
2, 5, 12, 31, 86....
246
249
252
255
258
HintThree is a magic number!
Hide
Answer
The answer is 249.
3^0 + 1 = 2
3^1 + 2 = 5
3^2 + 3 = 12
3^3 + 4 = 31
3^4 + 5 = 86
3^5 + 6 = 249
Hide
Comments
jdnorway
May 03, 2002
 No, it's 249. 
chamber44
May 20, 2002
 I might have gotten the answer if it was listed. The CORRECT answer is 249. Quit posting without double checking your work. 3^3+4=31 NOT 86. And 3^4+5=86 NOT 248. JDNOWAY is right. 
madade
Jun 29, 2002
 I agree with the others this is a poor example of posting any old rubbish. 
(user deleted)
Aug 31, 2002
 It appears that cathalmcabe is well adept at posting any old rubbish. almost all his teasers i have seen up to date are either totally incorrect of contain disputable facts. 
mathemagician
Apr 26, 2008
 2, 5, 12, 31, 86, ...
The differences {a2a1, a3a2,a4a3,a5a4,...} = {3, 7, 19, 55,... }
Now, {b2b1, b3b2, b4b3} =
{4, 12, 36, ... }
The last sequence is geometric with r=3, making the next term 108. Hence, b5b4 = 108 ; b5= 163; a6a5 = 163 , or a6 = 249. 
dalfamnest
Aug 24, 2010
 With the correction, it's not so bad! I worthwhile little challenge. You can also get the next number using "x3 1", "x3 3", "x3 5", etc 
Quocalimar
Feb 16, 2013
 i did this to get 258.
the final number times 2, plus the number before it.
Odd coincidence, or did you plan that? 
spikethru4
Feb 17, 2013
 Quocalimar, that doesn't even work. 2 x 86 + 31 = 203. Neither does it hold for the other numbers in the sequence.
Or am I misunderstanding you completely? 
eighsse
Aug 25, 2013
 Good one, I got it after the hint. Except I figured it this way, 3x1, 3x3, 3x5, 3x7....
Where x is each new number progressively. 
Wimm
Mar 03, 2015
 Nice, but I had the same solution as above (so 3x1, 3x3, 3x5, 3x7...). 
Back to Top
 

Follow Braingle!