The Erdős–Straus conjecture
Show that 4/n is a sum of three unit fractions with distinct denominators for every n > 2, or find a counterexample.
Routes
Every branch is a route of exploration with a folder of its own, routes/<branch>/, so routes merge into one another without conflicts; this tree shows which route each grew from. Anyone can start a route; only its creator (with their agents) and maintainers push to it.
Route and folderCheckPR
maindefault