Bug in LaguerreL Limit ?

Questions
, ,
1

I have found a bug in Limit.
I have Mathematica 10.0.1.0 on Windows 8.1.

plot.gif
plot.gif361Ă—215 3.73 KB

Limit[(n!*
      LaguerreL[
        n, -1]/(n^(n + 1/4)/Sqrt[2]/E^(n - 2 Sqrt[n] + 1/2)) - 
     1) Sqrt[n], n -> 1000] // N

Output: 0.649562

Limit[(n!*
      LaguerreL[
        n, -1]/(n^(n + 1/4)/Sqrt[2]/E^(n - 2 Sqrt[n] + 1/2)) - 
     1) Sqrt[n], n -> Infinity]

Output:13/16 = 0.8125

2

Sanstitre05.png
Sanstitre05.png667Ă—159 5.44 KB

3

Hi,

can confirm that on version 10.1 on OS X 10.10.3. Wolfram|Alpha gives the same as Limit-> Infinity in the front end:

ScreenShot2015-05-25at09.09.14.png
ScreenShot2015-05-25at09.09.14.png696Ă—143 8.85 KB

Cheers,

Marco

4

Yes, I get the same conflicting answers.

5

Thank you - this is a known issue and our teams are looking into it.

6

When you say “I have found a bug in Limit” do you mean you found it on another forum? If so, that should be mentioned explicitly, so as to avoid any appearance of claiming credit for another’s work.

7

I wanted to help him and other users.

Vaclav Kotesovec wrote:

I already reported this bug in 2012, but still was not fixed (in versions 7,8,9,10) Google Code Archive - Long-term storage for Google Code Project Hosting. see Issue 46.

Dr. Wolfgang Hintze wrote:

I see the question: why didn’t Wolfram solve the bug? Also it might be interesting information fo other users (like myself).

and now all clear.

8

Yes, all clear now. In future please remember to cite appropriately (that’s a general rule) and to mention when an issue is posted elsewhere (that can save readers time).

The bug, by the way, involves a subtle issue in Series code.