TheoremDB
All problems

[#P2612] Existence of a Costas array of order 32

Work on this problem in ChatGPT
An order-six Costas array, with one marked point in each row and column and segments joining every pair of points.
In this order-6 Costas array, no two joining segments have the same displacement vector.

Problem. Does there exist a permutation \(\pi\) of \(\{0,\ldots,31\}\) such that all displacement vectors \((j-i,\pi(j)-\pi(i))\), for \(0\le i<j<32\), are distinct?

1Remarks

Remark 1. Such a permutation is a Costas array of order 32.

Remark 2. For a fixed horizontal displacement d, the values pi(i+d)-pi(i) must be pairwise distinct.

2What counts as a solution

  • Give and directly verify a 32-entry Costas permutation, or exhaust all canonical permutations with a machine-checkable decomposition and no omitted symmetry class.

1Status

Current status (Existence at order 32 remains open). No verified order-32 Costas permutation or exhaustive nonexistence certificate was found in the audited primary literature.[1][3][4][5]

1Records

4 records

Notes and companion materialContext, examples, and computations

The search is finite, route-concentrated, and expensive enough that certified subtree exclusions would prevent substantial repeated work.

Original intake status. Vulakh and Finkel reported in 2022 that order 32 remained the smallest unresolved order. Status after that paper remains unverified.

  • Canonicalize complete arrays under the eight symmetries of the square before splitting the tree. Store used vertical differences separately for each horizontal displacement.
  • Trap: the square symmetries map corners to corners, so fixing pi(0)=0 restricts the search to arrays with a corner dot. Prefix counts under that restriction do not cover every symmetry class.

Recorded example 1. At order 6, [2,0,5,1,4,3] is a Costas permutation under zero-based indexing.

Computational notes

  • A fresh exact depth-first search in the corner-dot subclass fixed pi(0)=0 and enforced the Costas difference condition. The numbers of valid prefixes of lengths 2, 3, 4, 5, and 6 were 31, 915, 25655, 667122, and 16035001. These counts certify only that subclass.
How the 4 records connectTyped relations and evidence flow
How the records connect to the problem

ProblemExistence of a Costas array of order 32

2See also

How to cite

TheoremDB contributors, “Existence of a Costas array of order 32,” TheoremDB research memory, snapshot of July 25, 2026. https://theoremdb.org/statements/costas-array-order-32

This problem includes 4 records joined by 3 typed links, sourced from doi.org[1], current as of July 25, 2026.

1References

  1. Packet source. David Vulakh and Raphael Finkel, Parallel m-dimensional relative ant colony optimization (mDRACO) for the Costas-array problem, Soft Computing 26(12) (2022), 5765-5772. David Vulakh and Raphael Finkel, Parallel m-dimensional relative ant colony optimization (mDRACO) for the Costas-array problem, Soft Computing 26 (2022), 5765-5772, Conclusion and Appendix. scholarly publication · reference source · version of record · checked 2026-08-01Source use: citation only.Reports an order-32 heuristic search whose best permutation still has 17 Costas violations.Also cited at Vulakh and Finkel 2022, Conclusion and Appendix.Also cited at Vulakh and Finkel 2022, Section 4, page 5771, and Appendix: Arrays discovered.Source named by the research packet.
  2. Ken Taylor, Scott Rickard, and Konstantinos Drakakis, Costas Arrays: Survey, Standardization, and MATLAB Toolbox, ACM Transactions on Mathematical Software 37(4) (2011), Article 41, 31 pp. Survey definitions, construction taxonomy, and status tables. journal article · primary source · version of record · checked 2026-08-01Source use: original summary.Fixes the Costas-array definitions and construction taxonomy used to assess the order-32 status.
  3. Lutz Warnke, Bill Correll Jr., and Christopher N. Swanson, The Density of Costas Arrays Decays Exponentially, IEEE Transactions on Information Theory 69(1) (2023), 575-581. Introduction, Theorem 1, and Table I. journal article · primary source · author-hosted version of record checked 2026-07-26 · checked 2026-07-25Source use: citation only.Proves exponential decay of Costas-array density and supplies the enumeration context for the order-32 search.
  4. Fatih Gulec and Vahid Abolghasemi, Universal Costas Matrices: Towards a General Framework for Costas Array Construction, arXiv:2602.03407v1 (2026). Fatih Gulec and Vahid Abolghasemi, Universal Costas Matrices: Towards a General Framework for Costas Array Construction, 2026, Introduction and Table I. preprint · reference source · arXiv:2602.03407v1 · checked 2026-07-25Source use: citation only.Surveys standard Costas constructions and records the continuing gap at order 32.
  5. James K. Beard, Costas Arrays and Enumeration to Order 1030, IEEE DataPort (2017). IEEE DataPort database description, download index, and CC BY 4.0 notice. dataset · dataset source · dataset snapshot checked 2026-08-01 · checked 2026-07-25Source use: citation only.Provides the maintained Costas enumeration files checked for an order-32 witness and states their CC BY 4.0 terms.

CC0 candidate record assembled from a primary research paper and an independent prefix search.

Flag this problem

Report a problem

Your ChatGPT account

Opening ChatGPT

ChatGPT is opening in a new tab.