Collatz Crowd Hunt (3n + 1)

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What are we doing here?

The Collatz conjecture (the "3n + 1" problem)

Pick any whole number. If it's even, halve it. If it's odd, triple it and add one (3n + 1). Repeat forever. For example 6 → 3 → 10 → 5 → 16 → 8 → 4 → 2 → 1.

The conjecture says you always eventually land on 1 — no matter which number you start from. It's been checked for every number into the quintillions and always comes home. But nobody has proven it must, for every number, since it was posed in 1937. It's one of the most famous unsolved problems in mathematics.

What would break it

A single counterexample would disprove it — and there are only two kinds:

• A loop — a number that cycles back to itself, never reaching 1 (some other cycle than 4 → 2 → 1).
• A runaway — a number whose sequence climbs forever and never comes back down.

What this site does

We check the integers in order, from the highest verified point upward, handed out in blocks. For each number your browser runs the sequence only until it drops below where it started — which proves it reaches 1, since every smaller number is already verified — or until it catches a loop or a runaway. Most numbers settle in a few steps; the rare giant climb is where the math gets interesting (and the digits get huge).

Every block is independently re-run by 4 different people; only when their results match does it count. The big green number is the frontier: every integer below it is confirmed to reach 1.

Realistically this is a (fun, real) lottery ticket — almost certainly we'll just keep extending the verified record. But if a loop or runaway is ever found, the page lights up, and it's a genuinely historic discovery.