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