A staircase number is an (odd) number composed of one number added to the number less than it.
To find the staircase numbers for an odd value, we add one to the value then divide it by two. Then the number is equal to the result added to the result minus one.
Calculating this for the number we started with, would make two familiar values. Adding two side by side (t aligned) x values in e,1 and -f,1 would also make a staircase number.
When na is odd, what do you do to find an identifier for the element where the x is equal to one of the staircase numbers for na? And if na is even, for n-1?