sum of binomials .. bug ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg70486] sum of binomials .. bug ?*From*: yann_che2 at yahoo.fr*Date*: Tue, 17 Oct 2006 02:59:50 -0400 (EDT)

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

**Follow-Ups**:**Re: sum of binomials .. bug ?***From:*Devendra Kapadia <dkapadia@wolfram.com>