Re: sum of binomials .. bug ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg70490] Re: sum of binomials .. bug ?*From*: "ben" <benjamin.friedrich at gmail.com>*Date*: Wed, 18 Oct 2006 04:16:12 -0400 (EDT)*References*: <eh20si$2ms$1@smc.vnet.net>

Dear Yann, got the same bug on linux, even f[k_] := Sum[Binomial[2 - k, i], {i, 0, 1 - k}] x = 1; f[x] Clear[x]; f[x] /. x -> 1 gives wrong results. Bye Ben yann_che2 at yahoo.fr schrieb: > Hi everyone, > > on Mathematica 5.2 (mac os x), experimenting sums of binomials, i tried > the following: > > In[6]:= f[k_] := Sum[Binomial[21 - k, i], {i, 0, 10 - k}] > In[7]:= x = 3; f[x] > Out[7]:= 63004 > In[8]:= Clear[x] ; f[x] /. x -> 3 > Out[8]:= 262144 > In[9]:= Clear[x] ; f[x] > Out[9]:= 2^(21-x) > > > does anyone know why Out[7] and Out[8] give different results ? do you > think it is a bug ? i searched everywhere in the forums but couldn't > find anything that helped. > do you have a clue ? > > yann