How about: ?
Should be straightforward to prove it.
Let n be a positive integer, and R be the region defined by the simultaneous conditions x-y< n , x+y < n and x > 0. In terms of n
how many lattice points are contained in R?
If I didn't misunderstand the question I got 0 points for n=1 , 1 for n=2, 4 for n=3, 9 for n=4 . 16 for n=5.
How do I write this in terms of n?