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Coefficient

• To: mathgroup at yoda.ncsa.uiuc.edu
• Subject: Coefficient
• From: cfcgf at ux1.cts.eiu.edu (Chuck Fleming)
• Date: Sun, 9 Dec 90 10:43:06 CST

> I seem to be having a problem with the behaviour of Coefficient[] in
> Mathematica, namely if I have a series such as
>  
> sum = ... + a n + b + c/n +....
>  
> then Coefficient[sum,n] gives a, Coefficient[sum,1/n] gives c, but
> Coefficient[sum,1] does NOT give b, but zero instead! This is causing me
> problems, and I cannot see a simple work-around.

You might break up sum into two sums.  One with nonnegative powers of n and
one with negative powers of n.  Then Coefficient[posSum, n, i] will give the
coefficient of n^i including i=0. 

chuck fleming