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 A213271 #16 Oct 18 2019 13:30:49 %S A213271 0,1,2,2,18,42,66,168,300,910,1882,3192,5320,7166,8346,9042,7760,6668, %T A213271 4620,2822,1528,942,282,92,32,22,88,256,24 %N A213271 Costas arrays such that the corresponding permutation is a derangement. %C A213271 Fixed-point free permutations such that each row in the difference table consists of pairwise distinct elements (see example). %H A213271 Scott Rickard, <a href="http://costasarrays.org/">costasarrays.org</a> (information and papers about Costas arrays). %e A213271 The permutation (9, 8, 1, 6, 3, 7, 2, 4, 5) is a derangement and corresponds to a Costas array: %e A213271 9 8 1 6 3 7 2 4 5 (Permutation: p(1), p(2), p(3), ..., p(n) ) %e A213271 -1 -7 5 -3 4 -5 2 1 (step-1 differences: p(2)-p(1), p(3)-p(2), ... ) %e A213271 -8 -2 2 1 -1 -3 3 (step-2 differences: p(3)-p(1), p(4)-p(2), ... ) %e A213271 -3 -5 6 -4 1 -2 (step-3 differences: p(4)-p(1), p(5)-p(2), ... ) %e A213271 -6 -1 1 -2 2 ( etc. ) %e A213271 -2 -6 3 -1 %e A213271 -7 -4 4 %e A213271 -5 -3 %e A213271 -4 %Y A213271 Cf. A008404 (Costas arrays), A213270 (Costas arrays that are involutions), A213338 (Costas arrays that are cyclic), A213339 (Costas arrays that are connected). %K A213271 nonn,hard,more %O A213271 1,3 %A A213271 _Joerg Arndt_, Jun 08 2012