This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A001441 #27 Aug 02 2025 09:58:04 %S A001441 1,1,1,2,6,17,30,60,100,277,555,990,1616,2168,2467,2648,2294,1892, %T A001441 1283,810,446,259,114,25,12,8,29,89,23 %N A001441 Number of inequivalent Costas arrays of order n under dihedral group. %C A001441 Dihedral group of order 8 acts by rotations and reflections of the square. %D A001441 James K Beard, Jon C Russo, Keith Erickson, Michael Moneleone and Mike Wright, Combinatoric collaboration on Costas arrays and radar applications, Proceedings of the IEEE 2004 Radar Conference, April 26-29 2004, ISBN 0-7803-8234-X, pp. 260-265 (entries for orders 24 and 25). %D A001441 James K Beard, Jon C Russo, Keith Erickson, Michael Moneleone and Mike Wright,"Costas Array Generation and Search Methodology," to appear in IEEE Transactions on Aerospace and Electronic Engineering. (Order 26) %D A001441 CRC Handbook of Combinatorial Designs, C. Colbourn and J. Dinitz, Editors, 1996, IV.7: Costas Arrays by Herbert Taylor (IV.7.6, page 259, Table 2.29). %D A001441 CRC Standard Mathematical Tables and Formulae, 30th ed. 1996, p. 227 (contains errors). %H A001441 K. Drakakis, <a href="https://web.archive.org/web/20120206033140/http://www.costasarrays.org/Enumeration27TalkWeb.pdf">Results of the enumeration of Costas arrays of order 27</a>, Slides, 2008. %Y A001441 Cf. A008404, A001440, A001442, A008403. %K A001441 nonn,hard,more,nice %O A001441 1,4 %A A001441 _N. J. A. Sloane_ %E A001441 a(24)-a(26) from James K Beard (jkbeard(AT)comcast.net), Dec 04 2005 %E A001441 a(27) (from the Drakakis link) sent by John Healy (johnjhealy(AT)gmail.com), Jul 17 2008 %E A001441 a(28) and a(29) (from http://www.costasarrays.org/), _Joerg Arndt_, Jun 08 2012.