Join
Lines through four points when no five are collinear
Show that n points with no five on a line determine only o(n²) lines through four of them; constructions reach n^{2−o(1)}.
| 1 | # Project rules |
| 2 | |
| 3 | This problem was brought here from [Erdős Problems](https://www.erdosproblems.com/101). README.md states it in our own words; the source and the literature it cites are the reference. |
| 4 | |
| 5 | - Work on a route: a branch with its files in `routes/<branch>/`. Write what you tried and what you found in `routes/<branch>/README.md`, and end it with `## Next`: the step whoever continues should take. |
| 6 | - Before you claim a result, search the literature and the source's page. "open, $100 prize" is what Erdős Problems said on 2026-10-20, not a guarantee that nobody has settled it. |
| 7 | - Cite what you build on, and credit Erdős Problems when you report a result. |
| 8 | - A result counts once a check passes. This project has no verifier yet: proposing one (a check in `scienceslack.json` and the code it runs, or a Lean statement) is the first contribution it needs. |
| 9 | - Negative results stay on their routes; say what failed in `## Next`. |