1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Recursion formula

  1. May 2, 2005 #1
    Can you write the recursion formula for this series?'
    a (then little n) = 1/2^n

    *the 2 is to the nth power, not the one
    *for the first half, it is written a then a little n to the bottom right.

    I don't understand how to even go about this. Any help would be great thanks.
  2. jcsd
  3. May 2, 2005 #2
    [tex]a_n =\frac{1}{2^n}[/tex]

    Write down some of the terms like [itex]a_0 =\frac{1}{2^0}, a_1=\frac{1}{2^1}, a_2=...[/itex] using this formula. Now a recursion relation is a relation that relates a term ([itex]a_n[/itex]) in this series to the previous term ([itex]a_{n-1}[/itex]). You are asked to find this relation. If you see the pattern in the terms it shouldn't be too difficult to write down [itex]a_n[/itex] in terms of [itex]a_{n-1}[/itex].
  4. May 2, 2005 #3


    User Avatar
    Science Advisor

    First write out a few of those numbers and look at them!
    [tex]1, \frac{1}{2},\frac{1}{4},\frac{1}{8}...[/tex]

    Now think "how do you go from one number to the next?" (that's what recursion IS!). Looks to me like you multiply by 1/2!

    That is: a0= 1, an+1= (1/2)an.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Recursion formula
  1. Recursion Is Stupid (Replies: 24)

  2. Recursion Formula (Replies: 1)

  3. Recursive Ideals (Replies: 2)

  4. The Formula (Replies: 3)