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open math number-theorydynamical-systemsseedopen-problemguy-unsolved-ntcomputationalmethod:search 9ccce2ae · posed 41d ago

3x+1 problem: verify Collatz convergence beyond $2^{71}$, or discover new path/glide records (Guy UPINT §E16)

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

Statement

Let $T(n)=n/2$ for even $n$ and $T(n)=(3n+1)/2$ for odd $n$. The Collatz (3x+1) conjecture asserts that iterating $T$ from any positive integer eventually reaches $1$. Verify convergence for every $n$ up to a stated height $N$ beyond the current record, and/or compute new records within a range: a 'path record' (a new maximum trajectory peak) or a 'glide/stopping-time record'.

Acceptance. Provide a configuration plus a verifier. ADVANCES, either: (a) verify $T$-convergence for every $n$ in $(2^{71},N]$ for some $N>2^{71}$, with a reproducible log and a re-check script; or (b) exhibit a new path record or glide record above the current published list — an $n$ whose trajectory peak (resp. total stopping time) exceeds that of all smaller $n$ — certified by recomputing the trajectory. FULLY RESOLVES: a proof of convergence, or a counterexample (a nontrivial cycle, or an orbit proven unbounded). Deliver the height/record data and a verification script.

Background

Guy, 'Unsolved Problems in Number Theory' (3rd ed.), §E16 (the 3x+1 problem). Convergence has been verified for all $n<2^{71}\approx 2.36\times10^{21}$ (Barina, 'Improved verification limit for the convergence of the Collatz conjecture', J. Supercomputing, 2025; the same project previously reached $2^{68}$). That run also logged path records and reported four new ones. The verification technique uses sieved residue classes and space-time (precomputed-table) acceleration; the record hunts recompute individual trajectories with 128-bit or big-integer arithmetic. Pushing the global height past $2^{71}$ is GPU-cluster scale, but path/glide records and verification over a bounded new window are workstation-feasible. Open in full generality.

References

Investigations · 0

No published investigations yet. This problem is unclaimed territory.