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### Mathematic query

Posted: **Mon Dec 22, 2014 6:56 pm**

by **SimonAllen**

I have been testing out Mathematica in Raspbian and typed this

Sum[1/n^2,{n,infinity}]

In English this should sum the reciprocals of the squares i.e. 1 + 1/4 + 1/9 + 1/16 + 1/25 + 1/36 etc The surprising result should be pi^2/6 However Mathematica returns

HarmonicNumber[infinity, 2]

Why does it not produce the expected result?

### Re: Mathematic query

Posted: **Mon Dec 22, 2014 7:29 pm**

by **DougieLawson**

Are you running the latest version? There was a 500MB update for Wolfram on 6th August.

When I feed your intermediate result into the online W|A at

http://www.wolframalpha.com/input/?i=+H ... nity%2C+2] I get your expected result.

### Re: Mathematic query

Posted: **Mon Dec 22, 2014 7:31 pm**

by **jardino**

Try with a capital "I" on "Infinity" and let me know the result.

Perhaps this query should be in the "Mathematica" topic?

Regards.

### Re: Mathematic query

Posted: **Mon Dec 22, 2014 7:37 pm**

by **DougieLawson**

jardino wrote:Try with a capital "I" on "Infinity" and let me know the result.

Perhaps this query should be in the "Mathematica" topic?

Regards.

That worked on my version.

Code: Select all

```
In[4]:= Sum[1/n^2,{n,Infinity}]
2
Pi
Out[4]= ---
6
In[5]:=
```

The intermediate result also works with a capital I.

Code: Select all

```
In[5]:= HarmonicNumber[Infinity, 2]
2
Pi
Out[5]= ---
6
In[6]:=
```

### Re: Mathematic query

Posted: **Mon Dec 22, 2014 11:20 pm**

by **SimonAllen**

Grateful thanks to you all. Yes the problem was the 'I' in 'infinity' I should have typed 'Infinity' I think Mathematica treats the lower case as a variable where with the initial capital letter it recognises Infinity as, I was going to say a value, for what it is. Correcting that produced the expected result. I am quite astonished that Mathematica came bundled in Raspbian, a most generous gift by Stephen Wolfram.

### Re: Mathematic query

Posted: **Sat Feb 07, 2015 3:31 am**

by **szhorvat**

All built-in symbols in Mathematica have names starting with a capital letter, no exception.

Infinity, Pi, I, E, all of them are capitalized.

This makes it easy to avoid conflicts with builtins when you create your own symbols: just use lowercase names for your own ones.

Also, all of these names are *symbols* in Mathematica. There's no distinction between variables, functions, keywords, etc. as in other languages. Everything is just a symbol. Some symbols, such as Infinity, have builtin definitions or interpretations.