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## 2, 5, 12, 31, 86....

Series teasers are where you try to complete the sequence of a series of letters, numbers or objects.

 Puzzle ID: #3752 Fun: (2.18) Difficulty: (2.38) Category: Series Submitted By: cathalmccabe Corrected By: shenqiang

What's the next number in this sequence?

2, 5, 12, 31, 86....

246
249
252
255
258

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 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. mad-ade 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 {a2-a1, a3-a2,a4-a3,a5-a4,...} = {3, 7, 19, 55,... } Now, {b2-b1, b3-b2, b4-b3} = {4, 12, 36, ... } The last sequence is geometric with r=3, making the next term 108. Hence, b5-b4 = 108 ; b5= 163; a6-a5 = 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, 3x-1, 3x-3, 3x-5, 3x-7.... Where x is each new number progressively.