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Every odd number below 1193 reaches one under the Syracuse map

Proved
syracuse_reaches_one_below_1193

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 1≤m≤11921 \le m \le 11921≤m≤1192 there is a k≥0k \ge 0k≥0 with Tk(m)=1T^k(m) = 1Tk(m)=1.

This is a finite verification: the 596596596 odd starting values below 119311931193 have orbits meeting only 961961961 distinct odd numbers in total, the largest being 835018350183501, and every one of these orbits terminates at 111.

Its role is to supply the small-value input to the margin criterion for excluding Syracuse cycles. Combined with the fact that a periodic point whose orbit reaches 111 must equal 111, it shows that no nontrivial Syracuse cycle contains a value below 119311931193, which in turn excludes every cycle of period at most 939393.

Preamble
import Mathlib
import Definitions.Def_syracuseStep
Formal statement
theorem syracuse_reaches_one_below_1193 (m : ℕ) (hm : 0 < m) (hodd : Odd m) (hle : m ≤ 1192) :
    ∃ k : ℕ, syracuseStep^[k] m = 1 := by sorry
Source
Collatz mission https://prove2.me/missions/2f34a49f-2016-4de2-9662-fcd1cc96cc67; extension of syracuse_small_reaches_one (686cc205-cac4-4284-b9dd-7afc4bd394ff) from bound 33 to bound 1192. Orbit data agrees with the standard 3x+1 tables, cf. J. C. Lagarias, The 3x+1 Problem and Its Generalizations, Amer. Math. Monthly 92 (1985), Section 2.

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