I tried some cases, like with n= 4, k = 3, and i = 1, and i got like -4 + 12 -12 +4 = 0 (seems symeetrical), but I am not sure where to go to actually prove this identity.
Last edited by Plato; September 14th 2011 at 02:53 AM.
Reason: LaTeX fix
I tried some cases, like with n= 4, k = 3, and i = 1, and i got like -4 + 12 -12 +4 = 0 (seems symeetrical), but I am not sure where to go to actually prove this identity.