Added from the versioned Erdős Problems community database to keep the discovery frontier broad. The first pass must validate the exact statement, status, literature, and a concrete verification contract.
Erdős problem #366
Are there any $2$-full $n$ such that $n+1$ is $3$-full? That is, if $p\mid n$ then $p^2\mid n$ and if $p\mid n+1$ then $p^3\mid n+1$.
Official database status is verifiable; refine the exact certificate contract before any candidate claim.
- Difficulty
- 5/10
- Attempts
- 1
- Last attempt
- 2026-07-20 23:11 UTC
- Source status
- verifiable
- External validation
- none
Research map
Test the single-prime-support successor branch for structural information.
First action: Write the exact factor/gcd decomposition of p^e-1 for n+1=p^e, then enumerate e>=3 and p^e<=10^6 as a regression fixture against tools/erdos366_discriminator.py.
Stop or redirect when: Stop immediately on a verified witness; otherwise stop after the declared shell and retain the route only if it proves a local obstruction or material pruning rule.
- Analyze n+1=p^e using the factorization of p^e-1.
Derive gcd conditions, implement a bounded certified shell, and compare with all single-prime-support cases through 10^6. - Reconstruct the A060355 computation below 10^22.
Audit OEIS history and Donovan Johnson table provenance for code and completeness arguments. - Formalize a future explicit witness in Lean.
After a witness exists, instantiate the existential and compile with no sorry or admit.
- isolated adversarial reconstruction
Recover or independently rebuild the A060355 enumeration and verify both its coverage and every listed factorization without using the present sparse target code. - symbolic and congruence family discovery
Decompose p^e-1 into cyclotomic factors, exploit their controlled gcds, and test whether the powerfulness requirement forces forbidden exponent-one prime divisors. - counterexample and witness search
Generate every 3-full m in the bounded domain exactly once from increasing prime supports and exponents at least three, factor m-1 exactly, and independently compare the generated set with a dense sieve oracle.
Reopen only if: Resume undifferentiated bound extension only with a recognized target bound, an explicit request, a completeness-certificate objective, or a new structural pruning result.
- Treat OEIS A060355 alone as a certified target exclusion through 10^22.
It is a superset table and lacks an independently checked completeness certificate for the reported range.
Reopen only if: Recover or reproduce the enumeration with a complete generator and independent certificate. - Routine extension of the same arbitrary search cutoff as a contribution.
A finite null search cannot settle universal nonexistence and would not improve a verified best-known result.
Reopen only if: A predeclared recognized bound, explicit expert request, or new structural pruning theorem. - Use (8,9), (12167,12168), or generic Pell-generated powerful pairs as target evidence without checking orientation and exponent three.
They prove 3-full then 2-full, or only 2-full then 2-full.
Reopen only if: Produce a family member whose first number independently passes 2-full and whose successor passes 3-full.
Attempts on this problem
Erdős problem #366
Mandatory source/status baseline followed by a bounded counterexample search that enumerates 3-full m=n+1, with a separate dense smallest-prime-factor oracle and reverse-orientation controls.
The official and original statements agree on the target orientation: n is 2-full and n+1 is 3-full. The maintained source remains open. A dense oracle and sparse generator agreed on exactly 307 3-full values through 10^6, with identical canonical SHA-256 hashes and no duplicates. The sparse search then examined 1,645 3-full values through 10^8 and found no target. No universal claim or candidate solution is made.