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Re: Hypergeometric1F1 polynomial

• To: mathgroup at smc.vnet.net
• Subject: [mg91448] Re: Hypergeometric1F1 polynomial
• From: "Alec Mihailovs" <alec at mihailovs.com>
• Date: Fri, 22 Aug 2008 03:11:53 -0400 (EDT)
• References: <g8je5u$a4n$1@smc.vnet.net> <48ADCC77.9070400@gmail.com> <DA73101988B04F9CAAD09D9816E75229@AlecPC> <22d35c5a0808212132x2413bd58pd700a1b5cdac9ae4@mail.gmail.com>

> The polynomial form you are expecting (see In[1]) can be obtained by
> taking the series expansion about x == 0 to the order n (see In[2]).

Well, I can obtain it even without series expansion. For example, as

In[3]:= Hypergeometric1F1[-1, -2, 2 x]

Out[3]= 1 + x

The problem is that the answers given by Mathematica to the Sum problem, are 
not the same - they are not polynomials, with the series expansion, or 
without.

Alec