How Do Simple Programs Behave?

Note (c) for How Do Simple Programs Behave?…The first n elements can be found efficiently using Module[{a = 1}, Table[First[IntegerDigits[ a, a = BitXor[a, BitOr[2a, 4a]]; 2, i]], {i, n}]] The sequence does not repeat in at least its first million steps, and I would amazed if it ever repeats, but as of now I know of no rigorous proof of this. ( Erica Jen showed in 1986 that no pair of columns can ever repeat, and the arguments on page 1087 suggest that neither can the center column together with occasional neighboring cells.)

Note (a) for How Do Simple Programs Behave?

Note (a) for How Do Simple Programs Behave?

Note (a) for How Do Simple Programs Behave?

Note (a) for How Do Simple Programs Behave?

Note (a) for How Do Simple Programs Behave?

Note (a) for How Do Simple Programs Behave?

Note (a) for How Do Simple Programs Behave?

Note (c) for How Do Simple Programs Behave?