Re: Why won't this sum evaluate?

*To*: mathgroup at smc.vnet.net*Subject*: [mg120594] Re: Why won't this sum evaluate?*From*: Gary Wardall <gwardall at gmail.com>*Date*: Sat, 30 Jul 2011 06:01:42 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j0oopr$kse$1@smc.vnet.net>

On Jul 27, 5:20 am, PAR123 <reiser.p... at gmail.com> wrote: > In[120]:= $Version > Out[120]= "7.0 for Mac OS X x86 (32-bit) (January 30, 2009)" > > In[122]:= Sum[c^n/(1 + c^(2*n)), {n, 1, Infinity}] > Out[122]= -(1/4) + 1/4 EllipticTheta[3, 0, c]^2 > > In[123]:= Sum[c^n/(1 + c^(2*n)), {n, 0, Infinity}] > Out[123]= (won't simplify) > > The only thing different in the two sums is that the second sum is from 0 to Infinity rather than 1 to Infinity. Clearly, the n=zero term is 1/2. > > I have tried various Regularizations and Methods, (not exhaustively) but none seem to work on either of the sums, much less the last. > > A side problem - Is there a way to determine what Regularization and Method were used when none were specified? > > Thanks I'm using the latest Mac version 8 and I get the same results as you do. Gary Wardall

**Follow-Ups**:**Re: Why won't this sum evaluate?***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>