`Compfiles/Imo1981P6.lean`

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3 declarations, 0 contain sorry, 0 declared as axioms

International Mathematical Olympiad 1981, Problem 6

Suppose that f : ℕ × ℕ → ℕ satisfies

f (0, y) = y + 1
f (x + 1, 0) = f (x, 1),
f (x + 1, y + 1) = f (x, f (x + 1, y))

for all x y ∈ ℕ.

Determine f (4, 1981).

Imports (2)

Imported by 1 file

Compfiles.lean

def Imo1981P6.no_eval Wrapper to prevent the Lean kernel from eagerly trying to normalize the solution value, which happens to be way too large to normalize line 39 source
Source documentation
Wrapper to prevent the Lean kernel from eagerly trying to normalize the solution value, which happens to be way too large to normalize.

no axioms what this means
Statement uses: Nat
```
def no_eval (x : ℕ) : ℕ := x
…
```
determine Imo1981P6.solution_value line 43 source
standard axioms: propext what this means
Statement uses: Nat
Proof uses: Imo1981P6.no_eval, HSub.hSub, Nat.iterate, HPow.hPow, OfNat.ofNat
7 instances, coercions and auxiliary constants left out.
problem Imo1981P6.imo1981_p6 line 45 source
standard axioms: Classical.choice, Quot.sound, propext what this means
Statement uses: Nat, Eq, OfNat.ofNat, HAdd.hAdd, Imo1981P6.solution_value
Proof uses: Nat.strongRecOn, LT.lt, Nat.casesAuxOn, of_eq_true, Eq.trans, True, congr, congrArg, zero_add, eq_self, Eq.symm, Eq.mpr, id, Nat.lt_add_one, Eq.refl, HMul.hMul, Nat.recAux, congrFun', MulZeroClass.mul_zero, Mathlib.Tactic.Ring.of_eq and 33 more
50 instances, coercions and auxiliary constants left out.

Tactic trace: 42 steps
Open to load the checked before-and-after goal states.