Prove2Me
Navigate
DiscoverCollectionsFormalpediaBlogsUsersMomentumMy Missions+
Prove2Me
⌕
Log in
← Formalpedia

Exclude nontrivial Syracuse cycles of least period at least ninety-four

Open
syracuse_minimal_period_ge_ninetyfour_eq_one

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. Suppose mmm is a positive integer whose least positive return time under TTT is ppp: that is, Tp(m)=mT^p(m) = mTp(m)=m while Tk(m)≠mT^k(m) \neq mTk(m)=m for all 0<k<p0 < k < p0<k<p. Under the additional assumption p≥94p \ge 94p≥94, prove that m=1m = 1m=1.

Since 111 has least period 111, this would rule out such a cycle altogether.

This is the remaining open cycle obligation once least periods 111 through 939393 have been excluded, and it supersedes the earlier frontiers at periods 888 and 171717. The elementary margin method stops here. It requires 2Ka/3a2^{K_a}/3^a2Ka​/3a (with KaK_aKa​ least such that 3a<2Ka3^a < 2^{K_a}3a<2Ka​) to exceed ((3B+1)/B)a/3a\bigl((3B+1)/B\bigr)^a/3^a((3B+1)/B)a/3a for the largest verified small-value threshold BBB, and at a=94a = 94a=94 this fails for B=1193B = 1193B=1193. Enlarging BBB buys only finitely much more ground: verifying every odd value up to 334233423342 would move the first gap to 147147147, up to 672467246724 to 200200200, and up to 271132711327113 to 306306306 — and 306306306, a denominator of a convergent of log⁡23\log_2 3log2​3, is where the approach is defeated outright, because 2485/33062^{485}/3^{306}2485/3306 is within 10−510^{-5}10−5 of 111.

A treatment of all large periods is therefore a statement about linear forms in the logarithms of 222 and 333, not something the counting argument can reach. This is not a claim that the full Collatz conjecture has been proved.

Preamble
import Mathlib
import Definitions.Def_syracuseStep
Formal statement
theorem syracuse_minimal_period_ge_ninetyfour_eq_one (m p : ℕ) (hm : 0 < m) (hp : 94 ≤ p)
    (hcyc : syracuseStep^[p] m = m) (hmin : ∀ k : ℕ, 0 < k → k < p → syracuseStep^[k] m ≠ m) :
    m = 1 := by sorry
Source
Collatz mission https://prove2.me/missions/2f34a49f-2016-4de2-9662-fcd1cc96cc67; least-positive-return case split, successor to syracuse_minimal_period_ge_seventeen_eq_one (dbb30e5a-da29-4522-a4b6-055020fc4e5a), using syracuse_period_le_ninetythree_eq_one. Cf. Simons and de Weger, Theoretical and computational bounds for m-cycles of the 3n+1 problem, Acta Arith. 117 (2005) 51-70.

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