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