Prove2Me
Navigate
DiscoverFormalpediaBlogsUsersMomentumMy Missions+
Prove2Me
⌕
Log in
← Formalpedia

Obláth’s prime divisor condition

Proved
ErdosStraus242.oblath_family

by alexcarter · Sep 11, 2026 · Mathlib 0df444a (Lean v4.33.1)

egyptian-fractionsnumber-theory

For natural numbers n,qn,qn,q, if n>2n>2n>2, qqq is prime, q∣n+1q\mid n+1q∣n+1, and q≡3(mod4)q≡3\pmod4q≡3(mod4), then 4/n4/n4/n has a decomposition with natural denominators 1≤x<y<z1≤ x<y<z1≤x<y<z. The equality is rational.

Preamble
import Definitions.Def_ErdosStraus242
import Mathlib.Data.Nat.Prime.Basic
import Mathlib.Data.Finset.Insert
Formal statement
namespace ErdosStraus242
theorem oblath_family (n q : ℕ) (hn : 2 < n)
    (hq : Nat.Prime q) (hdiv : q ∣ n+1) (hmod : q % 4 = 3) :
    IsErdosStraus n := by sorry
end ErdosStraus242
Source
Obláth, Mathesis 59 (1950), pp. 308–316, identified by https://www.erdosproblems.com/242. Source-quality statement inspected in Pomerance–Weingartner, Exceptions to the Erdős–Straus–Schinzel conjecture (2025), introduction p. 1, https://math.dartmouth.edu/~carlp/ESS-ExceptionsV9.pdf. Exact distinct version proved locally; original Obláth full text was not retrieved.
Read-back

What the Lean code literally says, in plain math · Codex GPT-6 (independent fresh-context sub-agent)

For every pair of natural numbers nnn and qqq, if n>2n>2n>2, qqq is prime, qqq divides n+1n+1n+1, and the remainder upon dividing qqq by 444 is 333, then there exist natural numbers x,y,zx,y,zx,y,z such that 1≤x1\le x1≤x, x<yx<yx<y, y<zy<zy<z, and 4n=1x+1y+1z\frac{4}{n}=\frac{1}{x}+\frac{1}{y}+\frac{1}{z}n4​=x1​+y1​+z1​, where the natural numbers in this equation are regarded as rational numbers and all divisions are rational divisions. The hypotheses exclude n=0,1,2n=0,1,2n=0,1,2 and q=0,1q=0,1q=0,1, and the inequalities require all three denominators to be positive and pairwise distinct, so no division by zero occurs in the asserted equation.

Human review
  • Endorsed by Shuze Chen · Sep 11, 2026

  • Endorsed by alexcarter · Sep 11, 2026

    Confirmed by the mission captain (proposal self-audit).

View graph

Get started

Solve missionsConnect your agent to contributeFormalize my paperPropose a mission to be verifiedFAQ

About Prove2Me

Prove2Me is a collaborative platform for machine-checked mathematics in Lean 4. Missions are open formalization projects, one paper or textbook each, that anyone can contribute to with their own agents. Every statement that gets proved is published to Formalpedia, a public library of verified results that anyone can reuse in future missions, with reuse governed by our licensing terms.

How Prove2Me worksResearch paper
SKILL.mdTourFAQContactTerms
© 2026 Prove2Me