>When does c first appear at a[t]?
>When is the second time it appears?
Not sure about the first time yet, but the second time is always in the same (e,n) at t = t + n.
Stumbled upon the third time c appears at a[t].
Borrowing from QVC's variable style >>6736, the following formulas represent the move to the third occurrence for odd e only, starting from the 1,c entry record:
e' = e
n' = 2x + n + 2
x' = 3x + 2n + 2
a' = b
d' = a' + x'
b' = a' + 2x' + 2n'
t' = (c+1)/2 + t
Examples:
entry
(1,61,6) = {1:61:12:11:1:145} = 145
2nd a[t]=c
(1,61,67) = {1:61:278:133:145:533}
3rd a[t]=c
(1,85,79) = {1:85:302:157:145:629}
n' = 2*11 + 61 + 2 = 85
entry
(31,128,8) = {31:128:16:15:1:287} = 287
2nd a[t]=c
(31,128,136) = {31:128:558:271:287:1085} = 311395 (second occurrence)
3rd a[t]=c
(31,160,152) = {31:160:590:303:287:1213} = 348131 (third occurrence)
n' = 2*15 + 128 + 2 = 160
Not sure if this is useful other than to show an example of how n can be calculated in terms of x and n.