Closed form for $sum_{n=1}^infty log(n) * x^n$
$begingroup$
As in the title, I'm in
quest for $sum_{n=1}^infty log(n)cdot x^n$, where $0 le x lt 1$
Wolfram Alpha says: $-operatorname{PolyLog}^{(1, 0)}(0, x)$, but I don't understand what that means. (Of course, PolyLog stays for the polylogarithm).
Background
It's about "how many bits I need to encode a real number $0 < r < 1$ with a tolerance $delta/2$? The "naive" response is $-log_2(delta)$.
Nevertheless (long story short) I need a different approach:
I can encode every positive integer $n$ with approximately $Ccdotlog(n)$ bits
Let $0 < x_i < 1$ be a pseudo-random sequence, and let $N$ be the 1st index so that $r-delta/2 <x_N< r+delta/2$.
Then let's say that we can transmit $r$ via $N$ (with the tolerance $delta$). So we need $Ccdotlog(N)$ bits...But then I need the expected value
$E(Ccdotlog(N)) = sum_{n=1}^infty Ccdotlog(n)cdotdeltacdot(1-delta)^{n-1}$
$=Ccdot{deltaover1-delta} sum_{n=1}^infty log(n) cdot (1-delta)^n$
sequences-and-series summation logarithms
$endgroup$
|
show 1 more comment
$begingroup$
As in the title, I'm in
quest for $sum_{n=1}^infty log(n)cdot x^n$, where $0 le x lt 1$
Wolfram Alpha says: $-operatorname{PolyLog}^{(1, 0)}(0, x)$, but I don't understand what that means. (Of course, PolyLog stays for the polylogarithm).
Background
It's about "how many bits I need to encode a real number $0 < r < 1$ with a tolerance $delta/2$? The "naive" response is $-log_2(delta)$.
Nevertheless (long story short) I need a different approach:
I can encode every positive integer $n$ with approximately $Ccdotlog(n)$ bits
Let $0 < x_i < 1$ be a pseudo-random sequence, and let $N$ be the 1st index so that $r-delta/2 <x_N< r+delta/2$.
Then let's say that we can transmit $r$ via $N$ (with the tolerance $delta$). So we need $Ccdotlog(N)$ bits...But then I need the expected value
$E(Ccdotlog(N)) = sum_{n=1}^infty Ccdotlog(n)cdotdeltacdot(1-delta)^{n-1}$
$=Ccdot{deltaover1-delta} sum_{n=1}^infty log(n) cdot (1-delta)^n$
sequences-and-series summation logarithms
$endgroup$
$begingroup$
When you say "log" do you mean log base-10 or natural logarithm?
$endgroup$
– R. Burton
Dec 9 '18 at 18:01
$begingroup$
I suspect it has no closed form better than that. What do you need this for?
$endgroup$
– Ethan Bolker
Dec 9 '18 at 18:01
$begingroup$
Please edit the question to include a link to the Wolfram alpha output.
$endgroup$
– Shaun
Dec 9 '18 at 18:11
$begingroup$
@R.Burton natural logarithm
$endgroup$
– giuliolunati
Dec 9 '18 at 19:19
$begingroup$
@EthanBolker sorry, too long to explain now... maybe I'll edit the question.
$endgroup$
– giuliolunati
Dec 9 '18 at 19:30
|
show 1 more comment
$begingroup$
As in the title, I'm in
quest for $sum_{n=1}^infty log(n)cdot x^n$, where $0 le x lt 1$
Wolfram Alpha says: $-operatorname{PolyLog}^{(1, 0)}(0, x)$, but I don't understand what that means. (Of course, PolyLog stays for the polylogarithm).
Background
It's about "how many bits I need to encode a real number $0 < r < 1$ with a tolerance $delta/2$? The "naive" response is $-log_2(delta)$.
Nevertheless (long story short) I need a different approach:
I can encode every positive integer $n$ with approximately $Ccdotlog(n)$ bits
Let $0 < x_i < 1$ be a pseudo-random sequence, and let $N$ be the 1st index so that $r-delta/2 <x_N< r+delta/2$.
Then let's say that we can transmit $r$ via $N$ (with the tolerance $delta$). So we need $Ccdotlog(N)$ bits...But then I need the expected value
$E(Ccdotlog(N)) = sum_{n=1}^infty Ccdotlog(n)cdotdeltacdot(1-delta)^{n-1}$
$=Ccdot{deltaover1-delta} sum_{n=1}^infty log(n) cdot (1-delta)^n$
sequences-and-series summation logarithms
$endgroup$
As in the title, I'm in
quest for $sum_{n=1}^infty log(n)cdot x^n$, where $0 le x lt 1$
Wolfram Alpha says: $-operatorname{PolyLog}^{(1, 0)}(0, x)$, but I don't understand what that means. (Of course, PolyLog stays for the polylogarithm).
Background
It's about "how many bits I need to encode a real number $0 < r < 1$ with a tolerance $delta/2$? The "naive" response is $-log_2(delta)$.
Nevertheless (long story short) I need a different approach:
I can encode every positive integer $n$ with approximately $Ccdotlog(n)$ bits
Let $0 < x_i < 1$ be a pseudo-random sequence, and let $N$ be the 1st index so that $r-delta/2 <x_N< r+delta/2$.
Then let's say that we can transmit $r$ via $N$ (with the tolerance $delta$). So we need $Ccdotlog(N)$ bits...But then I need the expected value
$E(Ccdotlog(N)) = sum_{n=1}^infty Ccdotlog(n)cdotdeltacdot(1-delta)^{n-1}$
$=Ccdot{deltaover1-delta} sum_{n=1}^infty log(n) cdot (1-delta)^n$
sequences-and-series summation logarithms
sequences-and-series summation logarithms
edited Dec 9 '18 at 22:49
giuliolunati
asked Dec 9 '18 at 17:58
giuliolunatigiuliolunati
1013
1013
$begingroup$
When you say "log" do you mean log base-10 or natural logarithm?
$endgroup$
– R. Burton
Dec 9 '18 at 18:01
$begingroup$
I suspect it has no closed form better than that. What do you need this for?
$endgroup$
– Ethan Bolker
Dec 9 '18 at 18:01
$begingroup$
Please edit the question to include a link to the Wolfram alpha output.
$endgroup$
– Shaun
Dec 9 '18 at 18:11
$begingroup$
@R.Burton natural logarithm
$endgroup$
– giuliolunati
Dec 9 '18 at 19:19
$begingroup$
@EthanBolker sorry, too long to explain now... maybe I'll edit the question.
$endgroup$
– giuliolunati
Dec 9 '18 at 19:30
|
show 1 more comment
$begingroup$
When you say "log" do you mean log base-10 or natural logarithm?
$endgroup$
– R. Burton
Dec 9 '18 at 18:01
$begingroup$
I suspect it has no closed form better than that. What do you need this for?
$endgroup$
– Ethan Bolker
Dec 9 '18 at 18:01
$begingroup$
Please edit the question to include a link to the Wolfram alpha output.
$endgroup$
– Shaun
Dec 9 '18 at 18:11
$begingroup$
@R.Burton natural logarithm
$endgroup$
– giuliolunati
Dec 9 '18 at 19:19
$begingroup$
@EthanBolker sorry, too long to explain now... maybe I'll edit the question.
$endgroup$
– giuliolunati
Dec 9 '18 at 19:30
$begingroup$
When you say "log" do you mean log base-10 or natural logarithm?
$endgroup$
– R. Burton
Dec 9 '18 at 18:01
$begingroup$
When you say "log" do you mean log base-10 or natural logarithm?
$endgroup$
– R. Burton
Dec 9 '18 at 18:01
$begingroup$
I suspect it has no closed form better than that. What do you need this for?
$endgroup$
– Ethan Bolker
Dec 9 '18 at 18:01
$begingroup$
I suspect it has no closed form better than that. What do you need this for?
$endgroup$
– Ethan Bolker
Dec 9 '18 at 18:01
$begingroup$
Please edit the question to include a link to the Wolfram alpha output.
$endgroup$
– Shaun
Dec 9 '18 at 18:11
$begingroup$
Please edit the question to include a link to the Wolfram alpha output.
$endgroup$
– Shaun
Dec 9 '18 at 18:11
$begingroup$
@R.Burton natural logarithm
$endgroup$
– giuliolunati
Dec 9 '18 at 19:19
$begingroup$
@R.Burton natural logarithm
$endgroup$
– giuliolunati
Dec 9 '18 at 19:19
$begingroup$
@EthanBolker sorry, too long to explain now... maybe I'll edit the question.
$endgroup$
– giuliolunati
Dec 9 '18 at 19:30
$begingroup$
@EthanBolker sorry, too long to explain now... maybe I'll edit the question.
$endgroup$
– giuliolunati
Dec 9 '18 at 19:30
|
show 1 more comment
2 Answers
2
active
oldest
votes
$begingroup$
Definition of Polylogarithm:
http://mathworld.wolfram.com/Polylogarithm.html
No closed form exists in terms of elementary functions (addition, multiplication, powers, etc.), at least not in terms of real functions. You might be able to write it as a complex-valued function or improper integral.
Given that the polylogarithm is already a special function, I suspect that any closed form will be in terms of special functions rather than something nice.
$endgroup$
$begingroup$
Yes, I read that, so I'd understand what $PolyLog(0,q)$ means. What I don't understand is the "exponent" $^{(1,0)}$
$endgroup$
– giuliolunati
Dec 9 '18 at 19:38
$begingroup$
After working on it for a bit, I don't think that your sum has anything to do with polylogarithms at all. I have no idea what "$-PolyLog^{(1,0)}(0,x)$" is supposed to mean; it might be an error. Either way, The closest I can get to approximating the curve without spending more time on it is approximately $frac{x^2}{1.2-x^2}$.
$endgroup$
– R. Burton
Dec 9 '18 at 21:32
$begingroup$
Thank you for spending time on that! Where that approximation come from?
$endgroup$
– giuliolunati
Dec 9 '18 at 22:09
$begingroup$
Wild guess based on the form of the graph (which is similar visually similar to to $frac{x^2}{(a-x)^2}$, then adjusting $a$ until I got as close to $sum_{n=1}^{1000 }log(n)x^n$ as possible.
$endgroup$
– R. Burton
Dec 9 '18 at 23:30
add a comment |
$begingroup$
Ok, I found here what the notation $f^{(1,0)}$ means in Wolfram Alpha: it's the derivative wrt the 1st variable.
So the response is $-frac{partial operatorname{Li}(s,t)}{partial s}bigg|_{(s=0, t=x)}$
$endgroup$
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Definition of Polylogarithm:
http://mathworld.wolfram.com/Polylogarithm.html
No closed form exists in terms of elementary functions (addition, multiplication, powers, etc.), at least not in terms of real functions. You might be able to write it as a complex-valued function or improper integral.
Given that the polylogarithm is already a special function, I suspect that any closed form will be in terms of special functions rather than something nice.
$endgroup$
$begingroup$
Yes, I read that, so I'd understand what $PolyLog(0,q)$ means. What I don't understand is the "exponent" $^{(1,0)}$
$endgroup$
– giuliolunati
Dec 9 '18 at 19:38
$begingroup$
After working on it for a bit, I don't think that your sum has anything to do with polylogarithms at all. I have no idea what "$-PolyLog^{(1,0)}(0,x)$" is supposed to mean; it might be an error. Either way, The closest I can get to approximating the curve without spending more time on it is approximately $frac{x^2}{1.2-x^2}$.
$endgroup$
– R. Burton
Dec 9 '18 at 21:32
$begingroup$
Thank you for spending time on that! Where that approximation come from?
$endgroup$
– giuliolunati
Dec 9 '18 at 22:09
$begingroup$
Wild guess based on the form of the graph (which is similar visually similar to to $frac{x^2}{(a-x)^2}$, then adjusting $a$ until I got as close to $sum_{n=1}^{1000 }log(n)x^n$ as possible.
$endgroup$
– R. Burton
Dec 9 '18 at 23:30
add a comment |
$begingroup$
Definition of Polylogarithm:
http://mathworld.wolfram.com/Polylogarithm.html
No closed form exists in terms of elementary functions (addition, multiplication, powers, etc.), at least not in terms of real functions. You might be able to write it as a complex-valued function or improper integral.
Given that the polylogarithm is already a special function, I suspect that any closed form will be in terms of special functions rather than something nice.
$endgroup$
$begingroup$
Yes, I read that, so I'd understand what $PolyLog(0,q)$ means. What I don't understand is the "exponent" $^{(1,0)}$
$endgroup$
– giuliolunati
Dec 9 '18 at 19:38
$begingroup$
After working on it for a bit, I don't think that your sum has anything to do with polylogarithms at all. I have no idea what "$-PolyLog^{(1,0)}(0,x)$" is supposed to mean; it might be an error. Either way, The closest I can get to approximating the curve without spending more time on it is approximately $frac{x^2}{1.2-x^2}$.
$endgroup$
– R. Burton
Dec 9 '18 at 21:32
$begingroup$
Thank you for spending time on that! Where that approximation come from?
$endgroup$
– giuliolunati
Dec 9 '18 at 22:09
$begingroup$
Wild guess based on the form of the graph (which is similar visually similar to to $frac{x^2}{(a-x)^2}$, then adjusting $a$ until I got as close to $sum_{n=1}^{1000 }log(n)x^n$ as possible.
$endgroup$
– R. Burton
Dec 9 '18 at 23:30
add a comment |
$begingroup$
Definition of Polylogarithm:
http://mathworld.wolfram.com/Polylogarithm.html
No closed form exists in terms of elementary functions (addition, multiplication, powers, etc.), at least not in terms of real functions. You might be able to write it as a complex-valued function or improper integral.
Given that the polylogarithm is already a special function, I suspect that any closed form will be in terms of special functions rather than something nice.
$endgroup$
Definition of Polylogarithm:
http://mathworld.wolfram.com/Polylogarithm.html
No closed form exists in terms of elementary functions (addition, multiplication, powers, etc.), at least not in terms of real functions. You might be able to write it as a complex-valued function or improper integral.
Given that the polylogarithm is already a special function, I suspect that any closed form will be in terms of special functions rather than something nice.
answered Dec 9 '18 at 18:09
R. BurtonR. Burton
45619
45619
$begingroup$
Yes, I read that, so I'd understand what $PolyLog(0,q)$ means. What I don't understand is the "exponent" $^{(1,0)}$
$endgroup$
– giuliolunati
Dec 9 '18 at 19:38
$begingroup$
After working on it for a bit, I don't think that your sum has anything to do with polylogarithms at all. I have no idea what "$-PolyLog^{(1,0)}(0,x)$" is supposed to mean; it might be an error. Either way, The closest I can get to approximating the curve without spending more time on it is approximately $frac{x^2}{1.2-x^2}$.
$endgroup$
– R. Burton
Dec 9 '18 at 21:32
$begingroup$
Thank you for spending time on that! Where that approximation come from?
$endgroup$
– giuliolunati
Dec 9 '18 at 22:09
$begingroup$
Wild guess based on the form of the graph (which is similar visually similar to to $frac{x^2}{(a-x)^2}$, then adjusting $a$ until I got as close to $sum_{n=1}^{1000 }log(n)x^n$ as possible.
$endgroup$
– R. Burton
Dec 9 '18 at 23:30
add a comment |
$begingroup$
Yes, I read that, so I'd understand what $PolyLog(0,q)$ means. What I don't understand is the "exponent" $^{(1,0)}$
$endgroup$
– giuliolunati
Dec 9 '18 at 19:38
$begingroup$
After working on it for a bit, I don't think that your sum has anything to do with polylogarithms at all. I have no idea what "$-PolyLog^{(1,0)}(0,x)$" is supposed to mean; it might be an error. Either way, The closest I can get to approximating the curve without spending more time on it is approximately $frac{x^2}{1.2-x^2}$.
$endgroup$
– R. Burton
Dec 9 '18 at 21:32
$begingroup$
Thank you for spending time on that! Where that approximation come from?
$endgroup$
– giuliolunati
Dec 9 '18 at 22:09
$begingroup$
Wild guess based on the form of the graph (which is similar visually similar to to $frac{x^2}{(a-x)^2}$, then adjusting $a$ until I got as close to $sum_{n=1}^{1000 }log(n)x^n$ as possible.
$endgroup$
– R. Burton
Dec 9 '18 at 23:30
$begingroup$
Yes, I read that, so I'd understand what $PolyLog(0,q)$ means. What I don't understand is the "exponent" $^{(1,0)}$
$endgroup$
– giuliolunati
Dec 9 '18 at 19:38
$begingroup$
Yes, I read that, so I'd understand what $PolyLog(0,q)$ means. What I don't understand is the "exponent" $^{(1,0)}$
$endgroup$
– giuliolunati
Dec 9 '18 at 19:38
$begingroup$
After working on it for a bit, I don't think that your sum has anything to do with polylogarithms at all. I have no idea what "$-PolyLog^{(1,0)}(0,x)$" is supposed to mean; it might be an error. Either way, The closest I can get to approximating the curve without spending more time on it is approximately $frac{x^2}{1.2-x^2}$.
$endgroup$
– R. Burton
Dec 9 '18 at 21:32
$begingroup$
After working on it for a bit, I don't think that your sum has anything to do with polylogarithms at all. I have no idea what "$-PolyLog^{(1,0)}(0,x)$" is supposed to mean; it might be an error. Either way, The closest I can get to approximating the curve without spending more time on it is approximately $frac{x^2}{1.2-x^2}$.
$endgroup$
– R. Burton
Dec 9 '18 at 21:32
$begingroup$
Thank you for spending time on that! Where that approximation come from?
$endgroup$
– giuliolunati
Dec 9 '18 at 22:09
$begingroup$
Thank you for spending time on that! Where that approximation come from?
$endgroup$
– giuliolunati
Dec 9 '18 at 22:09
$begingroup$
Wild guess based on the form of the graph (which is similar visually similar to to $frac{x^2}{(a-x)^2}$, then adjusting $a$ until I got as close to $sum_{n=1}^{1000 }log(n)x^n$ as possible.
$endgroup$
– R. Burton
Dec 9 '18 at 23:30
$begingroup$
Wild guess based on the form of the graph (which is similar visually similar to to $frac{x^2}{(a-x)^2}$, then adjusting $a$ until I got as close to $sum_{n=1}^{1000 }log(n)x^n$ as possible.
$endgroup$
– R. Burton
Dec 9 '18 at 23:30
add a comment |
$begingroup$
Ok, I found here what the notation $f^{(1,0)}$ means in Wolfram Alpha: it's the derivative wrt the 1st variable.
So the response is $-frac{partial operatorname{Li}(s,t)}{partial s}bigg|_{(s=0, t=x)}$
$endgroup$
add a comment |
$begingroup$
Ok, I found here what the notation $f^{(1,0)}$ means in Wolfram Alpha: it's the derivative wrt the 1st variable.
So the response is $-frac{partial operatorname{Li}(s,t)}{partial s}bigg|_{(s=0, t=x)}$
$endgroup$
add a comment |
$begingroup$
Ok, I found here what the notation $f^{(1,0)}$ means in Wolfram Alpha: it's the derivative wrt the 1st variable.
So the response is $-frac{partial operatorname{Li}(s,t)}{partial s}bigg|_{(s=0, t=x)}$
$endgroup$
Ok, I found here what the notation $f^{(1,0)}$ means in Wolfram Alpha: it's the derivative wrt the 1st variable.
So the response is $-frac{partial operatorname{Li}(s,t)}{partial s}bigg|_{(s=0, t=x)}$
answered Dec 9 '18 at 22:47
giuliolunatigiuliolunati
1013
1013
add a comment |
add a comment |
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$begingroup$
When you say "log" do you mean log base-10 or natural logarithm?
$endgroup$
– R. Burton
Dec 9 '18 at 18:01
$begingroup$
I suspect it has no closed form better than that. What do you need this for?
$endgroup$
– Ethan Bolker
Dec 9 '18 at 18:01
$begingroup$
Please edit the question to include a link to the Wolfram alpha output.
$endgroup$
– Shaun
Dec 9 '18 at 18:11
$begingroup$
@R.Burton natural logarithm
$endgroup$
– giuliolunati
Dec 9 '18 at 19:19
$begingroup$
@EthanBolker sorry, too long to explain now... maybe I'll edit the question.
$endgroup$
– giuliolunati
Dec 9 '18 at 19:30