Just to nitpick it would be O(sqrt) as we do compute the sqrt of c to get d. That is the upper limit in the case you're describing.
I see the bit trimming as a means to simplify. When we trim bits we simply remove 2 as a factor, leaving us with factors beyond 2. I'm not sure why, but the number 2 appears to be "special" in the grid. Several times I've seen patterns where I expect the result to contain 2x2x…, but instead contain 2x… (One less factor of 2 than I expected).
I've said it before, but I suspect that VQC has been giving us hints related to all the keys he knows. The recursive one I suspect is one method. The triangle one is another and I suspect the (n-1)naa is a third.
How factorizing d and e solves it, I'm not sure. We know that if gcd(d, e) != 1, then we have the d = kq (for some k and q) and e = ko (for some k, o) which gives us: kqkq + ko =k(qq + o). I wonder if, when solving d and e we will end up with something similar that we can then use to "figure it out". It's the figure it out part that's hard and recusing over d and e doesn't give me any good ideas about how to solve it.
As for the subject, metacognition, I'm wonder what do we have? We have a huge grid, that exists as a lookup and we know that column 0 (row 1?) is supposed to operate as the QFT (Quantum Fourier Transformation), but just writing this doesn't make me understand it.
The grid shows us how numbers can be grouped together as the difference of two squares, and how this two squares are related to the integer and the integers factors.
We have patterns inside the grid for knowing how a cell is related to other cells in different columns. We can move in many ways, by shrinking or increasing the largest square we remove from the number. By transforming the number, but so far we haven't actually gotten a solution.