A Olympiad problem (original creation)
I have created many Olympiad problems, most of them for regional, state and National (Mexico) contests. This is not the one I'm proud the most, just one I find interesting and with a short solution.
(n,r) means nCr
Find all positive integers n,z,k that satisfy:
(n,0)^2+(n,1)^2+(n,2)^2+.....+(n,n)^2 = z^k
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