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First page of A Kernel-Certified Verification of the Erdős-Mollin-Walsh Conjecture below $10^{14}$

A Kernel-Certified Verification of the Erdős-Mollin-Walsh Conjecture below $10^{14}$

Ibrahim Mian, Shayaan Siddique

math.GM Jul 29, 2026 · v1 cs.LO
Proves in Lean 4 with Mathlib, via kernel-checked decide certificates, that no three consecutive powerful numbers exist below 10^12 and 10^14.
Erdős problem 364 asks whether three consecutive powerful numbers exist, where $n$ is powerful if $p \mid n$ implies $p^2 \mid n$. Erdős (1976) and, independently, Mollin and Walsh (1986) conjectured that none do; the $abc$ conjecture implies at most finitely many. The conjecture remains open. We present the first verification of the conjecture at any finite bound that is checked end to end by a proof kernel: machine-checked theorems in Lean 4 establishing that no triple of consecutive powerful numbers exists below $10^{12}$ and below $10^{14}$, with the axiom footprint of both theorems being exactly {propext, Classical.choice, Quot.sound} – no sorry, no native_decide, no trusted external computation. The statements are phrased in the byte-identical vocabulary of the google-deepmind/formal-conjectures formalization of the problem, and we prove abstractly that the open conjecture implies each bounded form, pinning the statement correspondence. The proof reduces the search to odd numbers via a mod-4 argument, represents every odd powerful number as $a^2 b^3$ with $a, b$ odd and $b$ squarefree, enumerates all odd powerful numbers by a fueled, kernel-reducible generator whose completeness is proved once and instantiated across 3,524 per-interval Boolean certificates, and eliminates the seven surviving distance-2 pairs (the members of OEIS A076445 below $10^{14}$) by explicit non-powerfulness witnesses. Every certificate's expected values are computed independently by a Python engine, so each kernel-checked equality doubles as a cross-implementation agreement. Total certified kernel time is roughly 46 CPU-hours. Larger uncertified computations exist (exhaustive to $10^{22}$; conditionally to about $7.38 \times 10^{28}$); our contribution is not a computational record but the elimination of trusted enumeration code from the evidence chain.

Erdős problem 364 conjectures that no three consecutive powerful numbers exist. Existing computational evidence, exhaustive to 10^22, relies on trusted, uncertified enumeration code.

The search is reduced to odd powerful pairs at distance 2 by a mod-4 argument. Odd powerful numbers are represented as a^2 b^3 with b squarefree and enumerated by a fueled, kernel-reducible generator whose completeness is proved once. That generator is used in 3,524 per-interval Boolean certificates checked by decide, without native_decide. The seven surviving pairs are eliminated with explicit non-powerfulness witnesses, and statements reuse the byte-identical Powerful definition from google-deepmind/formal-conjectures.

Lean theorems establish that no powerful triple exists below 10^12 and below 10^14, with axiom footprint exactly {propext, Classical.choice, Quot.sound}. Total certified kernel time is about 46 CPU-hours, and Python-computed expected values provide cross-implementation agreement.

X=10^12X=10^14
chunk certificates3203,204
kernel time57,652 s (~16 CPU-h)107,603 s (~30 CPU-h)
max single chunk~305 s61 s
pairs found57
Certified computation cost per bound