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What am I doing wrong?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91581] What am I doing wrong?
  • From: Jack L Goldberg 1 <jackgold at umich.edu>
  • Date: Thu, 28 Aug 2008 03:17:08 -0400 (EDT)

In(1)  SeriesCoefficient[1/(1-x),{x,0,n}]

Out(1)  (-1)^n*Binomial[-1,n]

Next,

In(2)   FunctionExpand[(-1)^n*Binomial[-1,n],Assumptions->Element[n,Integers]]

OUt(2)  ComplexInfinity

In(3)   Table[(-1)^n*Binomial[-1,n], {n,-2,2}]

Out(3)  {0,0,1,1,1}

Incidentally, FullSimplify in place of FunctionExpand yields the same  
result, ComplexInfinity.  I wonder if this misleading answer is a  
result of FunctionExpand and FullSymplify resorting to the Gamma  
Function for the simplification?

Is this a bug or a feature?

Thanks,

Jack


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