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@void4
Created August 4, 2024 21:44
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/-
Written by user "-d" from the https://bbchallenge.org/ Discord (https://discord.gg/3uqtPJA9Uv)
https://wiki.bbchallenge.org/wiki/BB(6)
Hydra:
https://wiki.bbchallenge.org/wiki/Hydra
https://bbchallenge.org/1RB3RB---3LA1RA_2LA3RA4LB0LB0LA
Antihydra:
https://wiki.bbchallenge.org/wiki/Antihydra
https://bbchallenge.org/1RB1RA_0LC1LE_1LD1LC_1LA0LB_1LF1RE_---0RA
-/
import Init.Data.Nat.Basic
import Mathlib.Data.Nat.Notation
import Mathlib.Data.Int.Notation
namespace bmo_p1
def f (ab : ℕ × ℕ) : ℕ × ℕ :=
let (a, b) := ab
if a ≥ b then
(a-b, 4*b+2)
else
(2*a+1, b-a)
theorem bmo_p1_halt : ∃ i, (let (a, b) := Nat.repeat f i (1, 2); a = b) := by
sorry
theorem bmo_p1_nonhalt : ∀ i, (let (a, b) := Nat.repeat f i (1, 2); a ≠ b) := by
sorry
end bmo_p1
namespace bmo_antihydra
def a (n : ℕ) : ℕ := match n with
| 0 => 8
| n+1 => a n * 3 / 2
def b (n : ℕ) : ℤ := match n with
| 0 => 0
| n+1 => b n + (if a n % 2 = 0 then 2 else -1)
theorem bmo_antihydra_halt : ∃ k, b k < 0 := by
sorry
theorem bmo_antihydra_nonhalt : ∀ k, b k ≥ 0 := by
sorry
end bmo_antihydra
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