Re: Puzzled by Sum
- To: mathgroup at smc.vnet.net
- Subject: [mg124646] Re: Puzzled by Sum
- From: Themis Matsoukas <tmatsoukas at me.com>
- Date: Sat, 28 Jan 2012 06:35:29 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
Yes, but:
A[i_, j_] := i/j + j/i
F[X_] := Module[{i, j}, Sum[A[X - j, j], {j, 1, X - 1}]]
F[X] /. X -> 2
F[i] /. i -> 2
2
-1 - 2 DifferenceRoot[
Function[{\[FormalY], \[FormalN]}, {(-2 + \[FormalN]) \[FormalY][\
\[FormalN]] + (3 - 2 \[FormalN]) \[FormalY][
1 + \[FormalN]] + (-1 + \[FormalN]) \[FormalY][
2 + \[FormalN]] == 0, \[FormalY][0] ==
0, \[FormalY][1] == -(1/2)}]][2]