diff --git a/FormalConjectures/ErdosProblems/372.lean b/FormalConjectures/ErdosProblems/372.lean new file mode 100644 index 0000000000..3f87cfd684 --- /dev/null +++ b/FormalConjectures/ErdosProblems/372.lean @@ -0,0 +1,41 @@ +/- +Copyright 2026 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.Attributes.Basic +import FormalConjecturesForMathlib.Data.Nat.MaxPrimeFac + +/-! +# Erdős Problem 372 + +*Reference:* [erdosproblems.com/372](https://www.erdosproblems.com/372) + +Conjectured by Erdős and Pomerance. Proved by Balog, who showed the stronger quantitative result +that this holds for $\gg \sqrt{x}$ many $n\leq x$, for all large $x$. +-/ + +namespace Erdos372 + +/-- +Let $P(n)$ denote the largest prime factor of $n$. There are infinitely many $n$ such that +$P(n)>P(n+1)>P(n+2)$. +-/ +@[category research solved, AMS 11] +theorem erdos_372 : + {n : ℕ | Nat.maxPrimeFac n > Nat.maxPrimeFac (n + 1) ∧ + Nat.maxPrimeFac (n + 1) > Nat.maxPrimeFac (n + 2)}.Infinite := by + sorry + +end Erdos372