Re: binomial sum bug

*To*: mathgroup at smc.vnet.net*Subject*: [mg82594] Re: binomial sum bug*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Fri, 26 Oct 2007 05:11:06 -0400 (EDT)*Organization*: The Open University, Milton Keynes, UK*References*: <ffpq7m$lf7$1@smc.vnet.net>

Jack Kennedy wrote: > In: Sum[Binomial[5,2k],{k,0,5}] > Out: 16 > > In: Sum[Binomial[n,2k],{k,0,n}] /. n->5 > Out: -16 > > What the? > > This has been addressed before > about a year ago and a work around was posted > but I have two questions: > > 1. Was it declared a bug by Wolfrram, and > 2. In general does Wolfram issue bug fixes, and specifically is there > a patch for this problem? > > $Version = 5.1 for Microsoft Windows (October 25, 2004) Apparently, this bug has not been fixed in version 5.2. Version 6.0.1 works as expected, however. In[1]:= Sum[Binomial[5, 2 k], {k, 0, 5}] Out[1]= 16 In[2]:= Sum[Binomial[n, 2 k], {k, 0, n}] /. n -> 5 Out[2]= 16 In[3]:= $Version Out[3]= "6.0 for Microsoft Windows (32-bit) (June 19, 2007)" (* Version 5.2 *) In[1]:= Sum[Binomial[5,2k],{k,0,5}] Out[1]= 16 In[2]:= Sum[Binomial[n,2k],{k,0,n}]/.n\[Rule]5 Out[2]= -16 In[3]:= $Version Out[3]= 5.2 for Microsoft Windows (June 20, 2005) Regards, -- Jean-Marc