from the baseball-hailstones-also-a-tough-problem dept.
mikejuk writes "A proof [preprint PDF] has been proposed for the Collatz conjecture about hailstone sequences. A hailstone sequence starts from any positive integer n the next number in the sequence is n/2 if n is even and 3n+1 if n is odd. The conjecture is that this simple sequence always ends in one. Simple to state but very difficult to prove and it has taken more than 60 years to get close to a solution."
"More software projects have gone awry for lack of calendar time than for all
other causes combined."
-- Fred Brooks, Jr., _The Mythical Man Month_