I'm trying to do parts d i) and ii) of following question:

http://www.cl.cam.ac.uk/teaching/exa...y2011p6q8A.pdf and have attached my attempt at a solution. I'm pretty sure my DFT is correct for i), but I can't seem to show that the power of the sequence is 1/2.

Any help would be greatly appreciated.

http://jgaming.co.uk/maths.jpg