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Conjecture Let
if
is odd and
if
is even. Let
. Assume we start with some number
and repeatedly take the
of the current number. Prove that no matter what the initial number is we eventually reach
.



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
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

This problem is also called Collatz conjecture, Ulam conjecture, or the Syracuse problem. For a more extensive discussion, visit the wikipedia article or [L].
Bibliography
[L] Jeffrey C. Lagarias: The 3x+1 problem: An annotated bibliography (1963--2000)
* indicates original appearance(s) of problem.