Number sequences hard

  1. Hello All,

    Well to make the Story short, I made a little bet in school that I could solve all the number sequences on a site, but now's the joke. I cant

    Ye ye , stop laughing But really I can handle myself at numbers normally pretty well, but this seems out of my league

    Can anyone solve this ?

    -2 3 27 69 129 …

    For those interested, this is the site, and was making the hard test ofc.

    3. The attempt at a solution

    It seems to be something like (x^n)-y

    help :-)
  2. jcsd
  3. You sure it doesnt start with -5?
  4. yes i am sure it doesnt start with -5 :)

    And I already mailed the website, but havent gotten any reply

    Have been cracking my brain on it for hours, it isn't funny anymore :(
    This is def. one of, if not the hardest test i made on the web lol.

    pwned :))
    Last edited: Mar 21, 2009
  5. Mark44

    Staff: Mentor

    I went to the site you posted and saw this problem among the hard problems group. The potential answers given are 178, 207, 268, and 312.

    I choose 207.

    Here's my reasoning:
    -2 = the starting number
    3 = 22 + (-1)
    27 = 52 + 2
    69 = 82 + 5
    129 = 112 + 8
    The pattern here seems to be that the number being squared increases by 3 each time, and the number added to the square also increases by 3 each time.
    The next number in the list should be
    142 + 11 = 196 + 11 = 207, which just happens to be one of the possible answers.
  6. You're Awesome!

    But doesnt taht make the start nuymber -3


  7. Mark44

    Staff: Mentor

    Well, there's that.

    Anyway, -2 = -3 for very small values of -2.:wink:
  8. These problems are all sort of dumb.

    For each sequence, there are infinitely many rule sets you can generate which will give you any answer you can possibly concoct. With no restrictions on the rules, the game is an exercise in futility.
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