Problem with Sum

*To*: mathgroup at smc.vnet.net*Subject*: [mg44004] Problem with Sum*From*: Mariusz Jankowski<mjankowski at usm.maine.edu>*Date*: Fri, 17 Oct 2003 05:14:29 -0400 (EDT)*Organization*: University of Maine System testbed server*Sender*: owner-wri-mathgroup at wolfram.com

Hello, can someone explain the following result: Sum[(-1)^m * (DiscreteDelta[1 - 2*m] - 2*DiscreteDelta[1 + 3*m]), {m, -Infinity, Infinity}] gives I + 2 (-1)^(2/3) Shouldn't the sum evaluate to zero, since for any value of m the summand is identically zero. Note that Sum[(-1)^m * (DiscreteDelta[1 - 2*m] - 2*DiscreteDelta[1 + 3*m]), {m, -10, 10}] returns 0, as expected. This looks like a bug, is it? Thanks, Mariusz