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Infinite Series Error - Bug? (again)

• To: mathgroup at smc.vnet.net
• Subject: [mg124572] Infinite Series Error - Bug? (again)
• From: clashton <clashton at gmail.com>
• Date: Wed, 25 Jan 2012 07:04:14 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Thanks to everyone who responded (not sure why I cannot see the
responses at the newsgroup).

Here is something peculiar:

Sum[q^(-6 + 4*n)/(1 - q^(-5 + 4*n)), {n, 0, Infinity}] /. {q -> 0.1}
gives an error, but

(Sum[q^(-6 + 4*n)/(1 - q^(-5 + 4*n)), {n, 0, 1}] /. {q ->
     0.1}) + (Sum[
    q^(-6 + 4*n)/(1 - q^(-5 + 4*n)), {n, 2, Infinity}] /. {q -> 0.1})
gives the correct answer
-21.1012