       Re: error with Sum and Infinity

• To: mathgroup at smc.vnet.net
• Subject: [mg102252] Re: [mg102245] error with Sum and Infinity
• From: Tomas Garza <tgarza10 at msn.com>
• Date: Mon, 3 Aug 2009 05:44:43 -0400 (EDT)
• References: <200908021001.GAA01730@smc.vnet.net>

```Hello, tb:

I suggest you use the following definition of t:

t[i_]:=If[i==3,1,0]

Then you'll get what you expect:

Sum[t[i],{i,1,10}]
Out= 1

In:= Sum[t[i],{i,1,Infinity}]
Out= 1

Tomas

> Date: Sun, 2 Aug 2009 06:01:39 -0400
> From: tommaso.biancalani at gmail.com
> Subject: [mg102245] error with Sum and Infinity
> To: mathgroup at smc.vnet.net
>
> Hi experts,
>
> i'm very new to Mathematica and this is my first problem. I define a
> function that is 0 everywhere:
> t[i_] := 0
> expect for point i =3 that is:
> t = 1
> If now i evaluate the finite sum i obtain 1 as expected
> Sum[ t[i], {i, 1, 10}]
> Out = 1
> but if i try do the same with infinity i obtain
> In:= Sum[ t[i], {i, 1, Infinity}]
> Out= 0
> instead of 1 expected. Any advice?
>
> tb
>

```

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