Re: Misbehaving Sum[..,{n,0,Infinity}]
- To: mathgroup at smc.vnet.net
- Subject: [mg37717] Re: Misbehaving Sum[..,{n,0,Infinity}]
- From: "David M. Wood" <dmwood at slate.Mines.EDU>
- Date: Sat, 9 Nov 2002 00:30:36 -0500 (EST)
- Organization: Colorado School of Mines
- References: <aqfpcb$7e1$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
David M. Wood <dmwood at slate.mines.edu> wrote:
> A nominally infinite sum for which only a finite number of terms
> contribute FAILS to evaluate for an uppper index limit of Infinity,
> but evaluates PROPERLY for an (arbitrary) finite upper index limit.
> Example:
> cn = If[n == 0, 1, 0] - 1/2 If[n == 1, 1, 0];
> Sum[x^(n-1) cn,{n,0,Infinity}]
> gives
> If[n == 0, 1, 0] - 1/2 If[n == 1, 1, 0]/((1 - x) x)
> while
> Sum[x^(n-1) cn,{n,0,731}]
> gives
> -1/2 + 1/x
Both Andrzej Kozlowski and Daniel Lichtblau were kind enough to respond
by e-mail, suggesting I use KroneckerDelta instead. This certainly works,
but maps my original query into a new one:
How can I persuade Mathematica to convert its conditionals (which were
generated by RSolve from a set of recursion relations) into KronckerDeltas
without carefuly human intervention?
Thanks once again.
--
David M. Wood, Dept. of Physics, Colorado School of Mines, Golden, CO 80401
Phone: (303) 273-3853; Fax: (303) 273-3919; e-mail: dmwood at Mines.EDU