arithmetic progression in c

Hi guys do have any ideas on how to make this arithmetic progression in c?
n^2 - m^2 - k^2 = aaa (a is any number)
for example 53^2 - 37^2 - 21^2 = 999
I need to find all the possible aaa's here

>>2
I think his specifications meant that it could be "a = 1" thus that "aaa = 111" or "a = 11" thus that "aaa = 111111."

Also, that looks painful.