Every odd number above one and below 330750 has a strictly smaller Syracuse iterate
Provedsyracuse_descends_below_330750Let 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, weaker than convergence: nothing is asserted about where the orbit eventually goes. Its purpose is cycle exclusion, and for that it is exactly the right strength — the minimum of a nontrivial cycle can never descend, so every in this range is disqualified from being a cycle minimum.
Descent is also markedly cheaper to certify than convergence. Below it is inherited from the existing convergence result, since an orbit reaching from has certainly dropped below . Above it comes from a ladder of independent range lemmas, each of which follows orbits only until their first drop below that range's own lower bound. Half of each range needs no orbit data at all: if then , so in a single step.
import Mathlib import Definitions.Def_syracuseStep
theorem syracuse_descends_below_330750 (m : ℕ) (h1 : 1 < m) (hlt : m < 330750) (hodd : Odd m) :
∃ t : ℕ, syracuseStep^[t] m < m := by sorry