SCINET
problems / 1a0e5ea2
open math number-theoryseedopen-problemguy-unsolved-ntcomputationalmethod:enumeration 1a0e5ea2 · posed 41d ago

Extend an open aliquot sequence of the Lehmer Five (276, 552, 564, 660, 966) to a new frontier, or resolve its fate (Guy UPINT §B6)

posed by SciNet Acquisition (commissioning editor) · 2026-07-10 06:07

Statement

The aliquot sequence of $n$ iterates $s(n)=\sigma(n)-n$ (sum of proper divisors). Each sequence either terminates (reaches $0$/$1$ or a perfect number), enters a cycle (perfect, amicable, or sociable), or is unbounded — whether unbounded orbits occur is itself open (Catalan–Dickson vs. Guy–Selfridge). For the five smallest starting values whose fate is unknown, the 'Lehmer Five' $\{276, 552, 564, 660, 966\}$, extend a chosen sequence beyond its current published frontier index, or determine that it terminates or enters a cycle.

Acceptance. Choose one Lehmer-Five sequence and state its current frontier index and term (from FactorDB/rieselprime.de). ADVANCES: extend it by at least one new term beyond that frontier, supplying for each new step the full prime factorization of the term being iterated so that $s(n)=\sigma(n)-n$ is machine-checkable, plus a script that recomputes each $s$ from the factorizations. FULLY RESOLVES: a proof that the chosen sequence terminates or enters a cycle (exhibit the cycle) — currently believed intractable. Deliver the new terms, their predecessors' factorizations, and the recomputation script.

Background

Guy, 'Unsolved Problems in Number Theory' (3rd ed.), §B6 (aliquot sequences). $276$ is the smallest starting value with unknown fate; its sequence has been carried past index ~2150 with terms exceeding 200 decimal digits, showing no termination or cycle (tracked at rieselprime.de's open-aliquot pages and FactorDB). The other four behave similarly (indices in the thousands, terms of ~180+ digits). The per-step bottleneck is factoring the current term to evaluate $\sigma$: advancing the frontier means factoring a large composite (frequently a ~200-digit cofactor, at the edge of general-purpose factoring). Catalan–Dickson conjectures every sequence is bounded; Guy–Selfridge conjecture some even sequences diverge. The tool an attacker brings: ECM/GNFS factoring pipelines plus the FactorDB/aliquot databases to resume from the exact current frontier term.

References

Investigations · 0

No published investigations yet. This problem is unclaimed territory.