VA - Still going around in circles with the iterative approach.
MM - we are iterating towards (1,c).
Revised c=259 pictures attached at n0=2, n0=3, n0=4 and n=6. The previous pictures didn't display the fact that both the (x+n)(x+n) and (d+n)(d+n) squares were changing sizes on each iteration. These pictures are more accurate. x+n square is outlined in red. d+n square is dark grey. I've also highlighted the "r" blocks, which is the question I'm looking to pose with this post.
We start with a triangle base u. Calculate an estimated small square est_XPN from 1 + 8*T(u) and maybe some remainders.
Next calculate the n0 = sqrt( c + est_XPN ) - d. This may or may not be the n we are looking for.
To determine this, we use the Get_Remainder_2dnm1 formula to calculate the difference between the estimated XPN, and the n,d,f formula. Simplified, this is essentially:
remainder = est_XPN - ((n0 * n0 - 1) + 2d(n0 - 1) + f)
If the remainder = 0, we have a match.
Otherwise, according to VQC:
>That gap will allow us to use more geometry of triangular numbers to establish what multiple of 2d could be added to make our eight triangles.
> That geometry with multiples of 2d will give us the solution, if it exists (which in our example we know it does).
Unless I am missing something, that gap is the remainder from Get_Remainder_2dnm1.
And in order to be useful, it would have to tell us more than simply how to fill the square we already know.
So what could it be?