True for all c where c is the difference of two squares. That includes the product of any two odd numbers. That includes the product of any two prime numbers.
That puts the row of the product of two prime numbers at rows n and n-1.
That difference is the key.
It means that columns -f and e have a property that can break the equation deadlock.
That property and those columns are unique to each c. They are dependent on d, e and therefore f.
As stated at the start, the square root of (D)avid and what remains are the key to unsealing the The End, the grid.
It will all make sense.
Especially the triangular part.
This is the beginning and The End.
I'm just a messenger.
This has always been about (you).