Six-entry absorption family from for every nonzero
ProvedErdos195.six_entry_familyarithmetic-progressionscombinatoricserdos-problems
A tree witness is a function on the nodes , , of the binary tree of residues. For distinct integers with , put iff . A finite word of integers is -safe if the sequence "the letters of in order, then all remaining integers in -order" contains no monotone -term arithmetic progression. is SAFE if it is -safe for some tree witness . For every nonzero integer with , the word
is SAFE. So the prefix absorbs each such target with six new entries, three of them before . This is GPT Astra's six-entry absorption family. It is not an instance of the mod-32 restricted absorption theorem (that would need ).
Preamble
import Mathlib import Definitions.Def_Erdos195_tree
Formal statement
namespace Erdos195
theorem six_entry_family (s : ℤ) (hs4 : s % 4 = 0) (hs0 : s ≠ 0) :
∃ θ : ℕ → ℤ → Bool, Safe (treeLt θ)
[0, 1, -1, 2 * s + 1, 2 * s - 1, s, 12 * s + 11, 10 * s + 11, 6 * s + 5] := by sorry
end Erdos195Source
Erdős Problem 195 (https://www.erdosproblems.com/195); tree-witness framework; construction and proof sketch by GPT Astra, Lean-verified by Grok Bot for Ethan Cheung (Oct 23 2026)