PPL 034 / 177 permanent IDsPrize Problem Ledger · PPLChecked 2026.07.26
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Prize Problem LedgerErdősPPL 034Erdős Problem #101

Permanent problem IDPPL 034

Verified openErdősconjecture

Geometry

Erdős Problem #101

Given n points in ℝ^2, no five of which are on a line, the number of lines containing four points is o(n^2).

geometry
01

The problem

Given n points in ℝ^2, no five of which are on a line, the number of lines containing four points is o(n^2).

Open since1974source estimate
Last checked2026.07.26Catalog verification
02

Reward offers

Offer 01$100Paul Erdős / Combinatorics Foundation
Documented

A solution must appear in a reputable journal, with documentation that Erdős offered the displayed amount. Claims are administered by the Combinatorics Foundation; erdosproblems.com does not pay awards.

Award source ↗Rules ↗
03

Sources & reading

3 unique reference linksCanonical problem page Claim or award rules OEIS A006065
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Related open targets

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