Some additional details, and perhaps some clarification, of how the different p formulas can be used to navigate the grid.
Attached pic shows a range of records in (1,145) for both positive and negative x.
The columns p and px represent "pointers" to other "t" values and are calculated as:
p column uses the formula "p+t".
px column uses the formula "p+1-t" for odd e, and "p+2-t" for even e.
In this case, the "p" value is being set to n. So the p column represents moves of 145 + t, and the px column represents moves of 145 + 1 - t.
The two records in the rectangle on the left are the 2nd and 3rd occurrences for a[t] = c, transformed by switching a and n (we can always do this because xx+e = 2na).
From there, the underlined p, px, and t values, show how we are currently able to jump between records using these p and px "pointers".
Within (1,145), there are 4 sequences or chains of records connected by a and b values.
These "pointer" values currently enable moving between 2 of the 4 sequences.
The ability to navigate to the first sequence would lead to a solution.