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06/10/13 2:11pm

In Response To 'Re: Re: Re: bug in Series[] function'
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Nope. Even deeper.

With the original definition for g, g with an undefined symbolic argument returns the argument.

In[6]:= g[n]

Out[6]= n

When the infinite Sum sees this, it becomes,

Sum[z^n*4*3^(n - 1), {n, 1, Infinity}]

===
Workaround:

Define g so it works only for numerical arguments and use NSum.

In[8]:= Clear[g]

In[9]:= g[n_Integer] := Sum[f[k], {k, 1, n}]

Now with undefined symbolic argument, g[ ..] returns the whole function call. This will give g another chance later if the output is used.

In[10]:= g[n]

Out[10]= g[n]

In[11]:= NSum[(2/10)^g[n]*4*3^(n - 1), {n, 1, Infinity}, WorkingPrecision -> 25]

Out[11]= 0.9158917783243623531876077

In[12]:= NSum[(2/10)^g[n]*4*3^(n - 1), {n, 1, 100}, WorkingPrecision -> 25]

Out[12]= 0.9158917783243623531876077


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Subject (listing for 'bug in Series[] function')
Author Date Posted
bug in Series[] function Eric Freden 06/03/13 2:31pm
Re: bug in Series[] function yehuda 06/06/13 09:50am
Re: Re: bug in Series[] function Eric Freden 06/06/13 11:44am
Re: Re: Re: bug in Series[] function Forum Modera... 06/07/13 4:59pm
Re: Re: Re: Re: bug in Series[] function Forum Modera... 06/10/13 2:11pm
Re: Re: Re: bug in Series[] function yehuda 06/08/13 2:22pm
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