       Re: Is it possible to impose a condition on an iterator of

• To: mathgroup at smc.vnet.net
• Subject: [mg101548] Re: [mg101499] Is it possible to impose a condition on an iterator of
• Date: Fri, 10 Jul 2009 06:42:10 -0400 (EDT)
• References: <200907090552.BAA16854@smc.vnet.net>

```In:= r1 = Sum[a^2 - 3*(a/(4*a^2)), {a, {1, 2, 3, 4, 5, 13, 14, 15, 16,
17,
18, 19, 20}}];

In:= r2 = Sum[a^2 - 3*(a/(4*a^2)), {a, DeleteCases[Range,
i_ /; i >= 6 && i <= 12]}];

In:= r3 = Sum[If[a >= 6 && a <= 12, 0, a^2 - 3*(a/(4*a^2))], {a, 1,
20}];

In:= r1 === r2 === r3
Out= True

In:= r1
Out= 64135524211/28217280

2009/7/9 Mauro <mauro at nonoyahoo.com>

> I would like to perform a summation of this type,
>
> Sum[a^2 - 3 a/(4 a^2), {a, 1, 20}]
>
> excluding however some values of the iteratore, I would for instance
> like to exclude the values than to greater of 6 and inferior to 12. Is
> it possible?
>
> Thanks
>
>

```

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