Syracuse descent for odd numbers between 1032607 and 1036607
Provedsyracuse_descends_range_1032607_1036607Let be the Syracuse map, sending to the odd part of . For every odd with , some iterate of falls strictly below :
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 — automatically below — instead of all the way to , and half the range needs no orbit data at all: if then , so in a single step. Only the residues require explicit data, here step facts.
This lemma is one stage of a ladder raising the cycle-minimum threshold from to . The stages are mutually independent — none imports another — so they may be checked in any order or concurrently.
import Mathlib import Definitions.Def_syracuseStep
theorem syracuse_descends_range_1032607_1036607 (m : ℕ) (hlo : 1032607 ≤ m) (hhi : m ≤ 1036607) (hodd : Odd m) :
∃ t : ℕ, syracuseStep^[t] m < m := by sorry