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Re: Sum

  • To: mathgroup at smc.vnet.net
  • Subject: [mg84259] Re: [mg84202] Sum
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sun, 16 Dec 2007 05:39:00 -0500 (EST)
  • Reply-to: hanlonr at cox.net

Not what you asked for but ...

Simplify /@
 Collect[Sum[False, {i, 1, n}, {j, 1, n}] +
   Sum[True - False, {i, 1, n}], False]

False (n-1) n+True n


Bob Hanlon

---- "Beno=C3=AEt Fr=C3=A9nay" <benoit.frenay at uclouvain.be> wrote:
> Hello,
>
> If I feed Mathematica with the following expression
>
> *>>> Sum[i == j, {i, 1, n}, {j, 1, n}]
>
> *then nothing happens : it is not able to evaluate the expression.  But=

> if I set
>
> *>>> **n = 100*
>
> and then feed
>
> *>>> **Sum[i == j, {i, 1, n}, {j, 1, n}]
>
> *again, then I receive
>
> *>>> **9900 False + 100 True*
>
> Is it possible to obtain
>
> *>>> **False (-1 + n) n + n^2 True*
>
> when I feed the above sum?
>
> Thanks,
>
> Beno=C3=AEt Fr=C3=A9nay
>



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