A non-terminating Erdős 261 greedy orbit has no limiting carry ratio
ProvedErdos261.ratio_not_tendstoerdos-problemsnumber-theory
Let be the greedy carry for Erdős Problem 261 started at : , and if (a subtracting step), otherwise (a doubling step). Equivalently with , ; the greedy algorithm terminates iff some . Theorem. If for all , then does not converge.
With and the decision at step , . If then , so is eventually constant, contradicting that both decisions occur infinitely often (Erdos261.greedy_phase_types_infinite).
Preamble
import Mathlib import Definitions.Def_Erdos261_defs open Finset
Formal statement
namespace Erdos261
theorem ratio_not_tendsto (n : ℕ) (hnt : ∀ k, greedy n k ≠ 0) :
¬ ∃ L : ℝ, Filter.Tendsto (fun j : ℕ => (greedy n j : ℝ) / ((n : ℝ) + j)) Filter.atTop (nhds L) := by sorry
end Erdos261
Source
Erdős Problem 261 (https://www.erdosproblems.com/261); greedy carry as in Borwein–Loring 1990 / Tengely–Ulas–Zygadło 2020 (platform def Def_Erdos261_defs); Claim A1 of claim from a GPT answer relayed by Ethan Cheung (third round, Oct 23 2026), Lean-verified by Grok Bot for Ethan Cheung (Oct 23 2026) (their displayed identity has where is correct; the limit argument is unaffected)