incorrect Sum[]
- To: mathgroup at smc.vnet.net
- Subject: [mg107571] incorrect Sum[]
- From: David Bevan <david.bevan at pb.com>
- Date: Wed, 17 Feb 2010 08:03:48 -0500 (EST)
Sum[] gets the following sum wrong: In[]:= f[n_,k_]:=-((2 (-1)^k n Pochhammer[1-2 n,-1+k])/k!) Note that f[n,k] is actually the same as Binomial[2n,k]. In[]:= Sum[f[n,k],{k,0,n}] Out[]= 4^n In[]:= Sum[f[n,k]/.n->5,{k,0,5}] Table[f[n,k]/.n->5,{k,0,5}] Total[%] Out[]= 638 Out[]= {1,10,45,120,210,252} Out[]= 638 In[]:= 4^5 Out[]= 1024 It gets the following correct: In[]:= Sum[f[n,k],{k,0,2n}] Out[]= 4^n I've forwarded this to submitabug. David %^> David Bevan Development Manager Pitney Bowes Emtex Software Tel: +44 (0)1923 279300 David.Bevan at pb.com