Legendary mathematician Paul Erdős once remarked that mathematics is not yet ready to solve the 3n 1 problem.
Known as the Collatz conjecture, it begins with a simple rule. Take any positive integer. If it is even, divide it by two. If it is odd, multiply it by three and add one. Repeat the process. The claim is that every starting number eventually reaches one.
Despite its simplicity, no complete proof exists. Yet modern progress offers strong hints. In 2019, Terence Tao showed that for almost all starting values, the sequence eventually drops significantly. This suggests that most trajectories do not grow without bound.
Probabilistic reasoning points in the same direction. On average, the sequence tends to shrink over time, making convergence to one highly likely.
Meanwhile, computers have verified the conjecture for numbers up to 2^68. Every tested case reaches one.
A simple problem, still unsolved, continues to challenge the limits of mathematics.