diff --git a/FormalConjectures/ErdosProblems/683.lean b/FormalConjectures/ErdosProblems/683.lean new file mode 100644 index 000000000..9006699a5 --- /dev/null +++ b/FormalConjectures/ErdosProblems/683.lean @@ -0,0 +1,68 @@ +/- +Copyright 2025 The Formal Conjectures Authors. + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + + https://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. +-/ + +import FormalConjectures.Util.ProblemImports + +/-! +# Erdős Problem 683 + +*References:* +- [erdosproblems.com/683](https://www.erdosproblems.com/683) +- [Er34] Erdős, Paul, A Theorem of Sylvester and Schur. J. London Math. Soc. (1934), 282--288. +- [Er55d] Erdős, P., On consecutive integers. Nieuw Arch. Wisk. (3) (1955), 124--128. +- [Er79d] Erdős, P., Some unconventional problems in number theory. Acta Math. Acad. Sci. Hungar. (1979), 71-80. +-/ + +namespace Erdos683 + +/-- +Let $P(n, k)$ be the largest prime factor of $\binom{n}{k}$. +-/ +def P (n k : ℕ) : ℕ := (n.choose k).primeFactors.sup id + +/-- +There exists $c > 0$ such that $P(n, k) > \min\{n-k+1, k^{1 + c}\}$ for all $0 \le k \le n$.} +-/ +@[category research open, AMS 11] +theorem erdos_683 : answer(sorry) ↔ + (∃ c > 0, ∀ n k : ℕ, 0 < k ∧ k < n → P n k > min (n - k + 1) (k ^ (1 + c))) := by + sorry + +/-- +Sylvester and Schur [Er34] proved that $P(n, k) > k$ for $k \le n/2$. +-/ +@[category research solved, AMS 11] +theorem erdos_683.variant.sylvester_schur : + ∀ n k : ℕ, 0 < k ∧ k ≤ n / 2 → P n k > k := by + sorry + +/-- +Erdos [Er55d] improved this to $P(n, k) \gg k \log k $ for $k \le n/2$. +-/ +@[category research solved, AMS 11] +theorem erdos_683.variant.erdos_log : + ∃ C > 0, ∀ n k : ℕ, 0 < k ∧ k ≤ n / 2 → P n k > C * k * Real.log k := by + sorry + +/-- +Standard heuristics suggest that $P(n, k) > e^{c\sqrt{k}}$ for some constant $c > 0$. +-/ +@[category research open, AMS 11] +theorem erdos_683.variant.exp_sqrt : + ∃ c > 0, ∀ n k : ℕ, 0 < k ∧ k ≤ n / 2 → P n k > Real.exp (c * Real.sqrt k) := by + sorry + +end Erdos683