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Re: Bug in SeriesCoefficient in 7.0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg98050] Re: Bug in SeriesCoefficient in 7.0
  • From: ADL <alberto.dilullo at tiscali.it>
  • Date: Sun, 29 Mar 2009 02:42:46 -0500 (EST)
  • References: <gqia68$okh$1@smc.vnet.net>

Given that the bug is there, a possible workaround in version 7 could
be to use FindSequenceFunction:

NC = 9; (* numeber of coefficients required *)

gf = FindSequenceFunction[
    Table[
        {n, SeriesCoefficient[Exp[-2*z]/(1 - z)^2, {z, 0, n}]},
        {n, 0, NC}
    ],
    n];

sgf = FullSimplify[gf, n \[Element] Integers]

====> (E^2*(-1)^n*2^(n + 2) + Gamma[n + 4, -2]) / (E^2*Gamma[n + 3])

If we call gf6 the coefficient form returned by Mathematica 6.01,
FullSimplify[gf6 - sgf] returns 0.

ADL


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