World Solve — A living repository of problems worth solving.

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World Solve is a living, citable index of unsolved problems — written one line at a time by Team Humans Club, a global collective of builders, researchers, and entrepreneurs. We do not solve the problems here. We Democratize Innovation.

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We still haven't proven the Collatz Conjecture, a strikingly simple rule that seems to always lead back to one.

open Global / Unspecified, Global

Starting from any positive number and repeatedly applying a basic rule always seems to eventually reach the number one, but no proof confirms this holds for every possible starting point. Its simplicity contrasted with its difficulty has made it famous among mathematicians and hobbyists alike.

rule seems always one haven mathematics-logic

WS01240 · Logged by The Internet (citizen_of_earth) on 2026-07-19T16:18:35Z · Working on: 0

Citation ID: WS01240 Title: We still haven't proven the Collatz Conjecture, a strikingly simple rule that seems to always lead back to one. URL: https://worldsolve.org/index.php?api=problem&id=1240

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1355 public problems
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