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Convergent sequence?

  1. Dec 17, 2009 #1
    i have a sequence an= t^n / (n factorial).
    I know that the infinite series of it converges to zero, but i need to know if the limit of an goes to zero or not , as n goes to infinity.

  2. jcsd
  3. Dec 17, 2009 #2
    are you sure about that? I think the series would converge to something like [tex]e^t[/tex], that is if you mean the series [tex]\sum_{0 \leq n} \frac{t^n}{n!}[/tex]

    if a series converges as you say, then its terms necessarily tend to 0
  4. Dec 17, 2009 #3


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    You probably mixed the things up: you know that a_n->0 as n->\infty (which is a necessary but not sufficient condition for the series to converge), and you wonder whether the series converges.
  5. Dec 17, 2009 #4
    yes... fo course if converges to the exponential function.

    and i just found a theorem, saying that it makes each term to vanish as well.

    thank you though.. i think sometimes i get confuesdif i spend too much time on one topic.
  6. Dec 17, 2009 #5
    there is one more thing....
    what if i start the sum from 1 or even some random constant k, will the sum of an= t^n / (n factorial) still go to the exponential function as n goes to infinity? i mean if we just consider the tail of the sequence, will the series still go to e^t?

    thank you
  7. Dec 17, 2009 #6


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    The series will will sum to et - all the terms you left out.
  8. Dec 17, 2009 #7
    thanks very much
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