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!

Homework Help: How to sum this series

  1. Nov 27, 2009 #1
    1. The problem statement, all variables and given/known data
    I just trying to sum this series, 1/(n!*n) n from 1 to infinity. also similar 1/(n!*n^2)

    2. Relevant equations


    3. The attempt at a solution
    I know[tex]\sum\frac{1}{n!}=e[/tex]

    My math technique is rusty, can any one help? thanks in advance. ciao
  2. jcsd
  3. Nov 27, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    The sum of 1/n isn't ln. It diverges. And both of those sums involve nasty non-elementary functions. I only know this because I looked them up. Why do you think you have to evaluate them exactly? A numerical approximation to both converges very rapidly.
  4. Nov 28, 2009 #3
    Thanks. I am doing study on statistics. On some topic I have sum up probabilities of infinite number of events. I have done numberical approximation with excel, and the result is equivalent to a specific event. I was trying to show why.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook