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A 2-adic constraint on the separable baseline.

Proved
HalfPlane.four_pow_omega_dvd_circleCount

by raver1975 · Sep 13, 2026 · Mathlib c5ea003 (Lean v4.30.0)

aether-catalogmachinelearning

A 2-adic constraint on the separable baseline. For odd squarefree N, 4^ω(N) divides C(N): every local factor p - χ_p(-1) is divisible by 4, since p ≡ 1 (mod 4) gives 4 ∣ p - 1 and p ≡ 3 (mod 4) gives 4 ∣ p + 1.

theorem HalfPlane.four_pow_omega_dvd_circleCount{N : ℕ} (hodd : ¬ 2 ∣ N) (hsq : Squarefree N) :
    4 ^ N.primeFactors.card ∣ circleCount N := by sorry

Formalization Note Transplanted verbatim from the Aether Catalog source MachineLearning/HalfPlaneClosedForm.lean; the statement is byte-identical to the source declaration, elaborated with autoImplicit disabled in the platform environment.

Preamble
-- Thm stub generated from MachineLearning/HalfPlaneClosedForm.lean
import Mathlib
import Definitions.Def_MachineLearning_HalfPlaneCircleBasic
import Definitions.Def_MachineLearning_HalfPlaneClosedForm
import Definitions.Def_MachineLearning_HalfPlaneSemiprime

/-!
# Cycle 4: the separable baseline in closed form

The circle count is an arithmetic function in the technical sense, and it is
multiplicative.  Combined with the odd-prime conic count this gives a closed
product formula for every odd squarefree modulus:

  `C(N) = ∏_{p ∣ N} (p - χ_p(-1))`.

This is the exact "free-witness / CRT-separable" baseline: `C` is computable from the
factorisation of `N` in `O(ω(N))` arithmetic operations, while the non-separable
half-plane count `H` studied in the other files admits no such product formula
(`halfPlaneCount_not_multiplicative`).
-/

open HalfPlane

open Finset
Formal statement
theorem HalfPlane.four_pow_omega_dvd_circleCount{N : ℕ} (hodd : ¬ 2 ∣ N) (hsq : Squarefree N) :
    4 ^ N.primeFactors.card ∣ circleCount N := by sorry
Source
https://github.com/paulklemstine/Lean/blob/53c2925a02/Catalog/MachineLearning/HalfPlaneClosedForm.lean#L68

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