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setting up infinite sequence and plotting

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Robert
Robert on 29 Jun 2024 at 20:02
Answered: Prathamesh on 5 Jul 2024 at 10:58
How do I set up and plot:
Sum (n=0 to infinity) (n^3+1)
Thank you
  1 Comment
John D'Errico
John D'Errico on 29 Jun 2024 at 20:31
Edited: John D'Errico on 29 Jun 2024 at 20:36
What have you tried? If nothing, then why not? Make an effort.
Of course, you may need to consider the series you show grows rapidly to infinity. So I might guess your question does not even show the series you actually want to form. Perhaps you mean the sum of 1/(n^3+1), not the sum of (n^3+1). That is convergent, apparently to:
vpa(ans)
ans =
1.6865033423386238859646052121869

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Answers (3)

sai charan sampara
sai charan sampara on 30 Jun 2024 at 8:21
Hello Robert,
I am assuming that you want to sum 1/(n^3+1) and not n^3+1 since the sum for n^3+1 tends to infinity as n moves to infinty. The sum of 1/(n^3+1) converges to a value as n tends to infinity. You can try doing this by calculating the value of the sum for each n value in a "while" loop. You can store the previous and current sum values. Then you can decide a tolerance value within which if there is no change you can accept the sum as converged value. It can be done similar to the code shown:
old_sum=sym(0);
new_sum=sym(1);
data=new_sum;
n=1;
tol=0.000001;
while((new_sum-old_sum)>tol)
old_sum=new_sum;
new_sum=new_sum+(1/(n^3+1));
n=n+1;
data=[data,new_sum];
end
vpa(old_sum)
ans = 
1.6864528398592121974925758815338
vpa(new_sum)
ans = 
1.6864538398582121984926371784164
plot(0:n-1,data)
You can decrease the "tol" (tolerance) value for more accurate results. Here is the link to documentation of "vpa":

tom
tom on 5 Jul 2024 at 9:16
  1. Define the Sequence: Decide on the mathematical formula or rule that generates the sequence.
  2. Generate Terms: Compute the terms of the sequence up to a reasonable number (since we can't truly generate an infinite number of terms).
  3. Plot the Sequence: Visualize the terms using a plot.
For demonstration, I'll consider a few common types of sequences and plot them:
  1. Arithmetic Sequence: A sequence in which each term after the first is obtained by adding a constant difference to the previous term. an=a+(n1)da_n = a + (n-1)dan=a+(n1)dwhere aaa is the first term and ddd is the common difference.
  2. Geometric Sequence: A sequence in which each term after the first is obtained by multiplying the previous term by a constant ratio. an=arn1a_n = ar^{n-1}an=arn1where aaa is the first term and rrr is the common ratio.
  3. Harmonic Sequence: A sequence in which each term is the reciprocal of an arithmetic sequence. an=1na_n = \frac{1}{n}an=n1
Let's plot the first 50 terms of each of these sequences.Arithmetic Sequence
  • First term a=1a = 1a=1
  • Common difference d=2d = 2d=2
Geometric Sequence
  • First term a=1a = 1a=1
  • Common ratio r=2r = 2r=2
Harmonic Sequence
  • an=1na_n = \frac{1}{n}an=n1
I'll generate and plot these sequences in Python.
Here are the plots for the three different types of sequences:
  1. Arithmetic Sequence (an=1+(n1)×2a_n = 1 + (n-1) \times 2an=1+(n1)×2): The terms increase linearly.
  2. Geometric Sequence (an=1×2(n1)a_n = 1 \times 2^{(n-1)}an=1×2(n1)): The terms increase exponentially.
  3. Harmonic Sequence (an=1na_n = \frac{1}{n}an=n1): The terms decrease and approach zero as nnn increases.

Prathamesh
Prathamesh on 5 Jul 2024 at 10:58
project in wed papge

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