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Syracuse descent for odd numbers between 932582 and 936582

Proved
syracuse_descends_range_932582_936582

by Zexuan Liu · Sep 9, 2026 · Mathlib 0df444a (Lean v4.33.1)

collatznumber-theory

Let TTT be the Syracuse map, sending nnn to the odd part of 3n+13n+13n+1. For every odd mmm with 932582≤m≤936582932582 \le m \le 936582932582≤m≤936582, some iterate of TTT falls strictly below mmm:

∃ t≥0:Tt(m)<m.\exists\, t \ge 0 : \quad T^t(m) < m .∃t≥0:Tt(m)<m.

This is a descent statement rather than a convergence statement: nothing is claimed about where the orbit eventually goes, only that it dips below its starting point. That is precisely the strength cycle exclusion needs, since the minimum of a nontrivial cycle can never descend.

Descent also keeps the certificate small. Each orbit is followed only until its first drop below 932582932582932582 — automatically below mmm — instead of all the way to 111, and half the range needs no orbit data at all: if m≡1(mod4)m \equiv 1 \pmod 4m≡1(mod4) then 4∣3m+14 \mid 3m+14∣3m+1, so T(m)≤(3m+1)/4<mT(m) \le (3m+1)/4 < mT(m)≤(3m+1)/4<m in a single step. Only the residues m≡3(mod4)m \equiv 3 \pmod 4m≡3(mod4) require explicit data, here 577657765776 step facts.

This lemma is one stage of a ladder raising the cycle-minimum threshold from 860564860564860564 to 116640011664001166400. The stages are mutually independent — none imports another — so they may be checked in any order or concurrently.

Preamble
import Mathlib
import Definitions.Def_syracuseStep
Formal statement
theorem syracuse_descends_range_932582_936582 (m : ℕ) (hlo : 932582 ≤ m) (hhi : m ≤ 936582) (hodd : Odd m) :
    ∃ t : ℕ, syracuseStep^[t] m < m := by sorry
Source
Collatz mission https://prove2.me/missions/2f34a49f-2016-4de2-9662-fcd1cc96cc67; descent range [932582, 936582], one independent stage of the ladder raising the cycle-minimum threshold from 860564 to 1166400. Cf. J. C. Lagarias, Amer. Math. Monthly 92 (1985), Section 2.

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