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Perron values have limsup at least two

Proved
Freiman.perron_frequently_at_least_two

by tp · Sep 9, 2026 · Mathlib 0df444a (Lean v4.33.1)

classical-spectracontinued-fractionsfreiman-hall-rayproof-graph

If digits at least two occur infinitely often, P_n exceeds those digits. Otherwise the eventual all-one tail gives P_n→sqrt 5>2, by the report’s cylinder continuity argument.

Preamble
import Definitions.Def_Freiman_perronArithmetic
Formal statement
namespace Freiman

theorem perron_frequently_at_least_two (b : ℕ → ℕ+) :
    ∀ ε : ℝ, 0 < ε → ∀ N : ℕ, ∃ n : ℕ, N ≤ n ∧ 2 - ε < perronValue b n := by
  sorry

end Freiman
Source
Freiman's Hall ray: Proof report and corrected English text, 8 September 2026, foundations.tex, §1.2, proof of found:perron

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