Results 1 to 4 of 4
Like Tree1Thanks
  • 1 Post By chiro

Math Help - Help with calculating geometric sequence

  1. #1
    Member
    Joined
    Nov 2012
    From
    israel
    Posts
    164
    Thanks
    2

    Help with calculating geometric sequence

    Hi,
    I hope it is the right place to post it...

    I need help with the following sequence:

    \sum_{i=0}^{j}2^{2^i}=N

    (it's 2 to the power of 2 to the power of i)

    I need to find i as a function of N.
    meaning how further away in the sequence do i need to go, in order to get N.

    any help would greatly appreciated.
    Last edited by Stormey; June 28th 2013 at 01:32 AM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2012
    From
    Australia
    Posts
    3,649
    Thanks
    601

    Re: Help with calculating geometric sequence

    Hey Stormey.

    Did you mean as a function of j?

    I don't know of a closed form solution but you should look into techniques like Euler-Mclaurin series and their relationship to integrals.
    Thanks from topsquark
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Nov 2012
    From
    israel
    Posts
    164
    Thanks
    2

    Re: Help with calculating geometric sequence

    Hi chiro.
    yes, as a function of j, sorry.
    the truth is that it is actually a question from data starctures in computer science, so I almost sure the solution suppose to be accomplished with discrete math.
    (using some manipulation to compute the sum of a more simple sequence, to which the sum is known or easy to calculate, and then calculating the sum of the original sequence,
    I also tried to think about some change of variable [index in this case], that will help simplify this problem)
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Sep 2012
    From
    Australia
    Posts
    3,649
    Thanks
    601

    Re: Help with calculating geometric sequence

    You might want to consider a bit-wise representation (i.e. binary) and how that relates to N.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. calculating limit of a sequence
    Posted in the Calculus Forum
    Replies: 2
    Last Post: December 30th 2012, 11:40 AM
  2. Replies: 4
    Last Post: May 13th 2012, 06:35 PM
  3. Replies: 0
    Last Post: March 6th 2011, 06:07 AM
  4. Replies: 2
    Last Post: January 23rd 2007, 08:47 AM
  5. Replies: 12
    Last Post: November 15th 2006, 12:51 PM

Search Tags


/mathhelpforum @mathhelpforum