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 A213339 #5 Jun 09 2012 04:54:12 %S A213339 1,1,2,6,26,80,152,348,628,1868,3870,7014,11788,15746,18388,19820, %T A213339 17218,14344,9844,6238,3430,1968,814,184,84,52,190,656,132 %N A213339 Costas arrays such that the corresponding permutation is connected. %H A213339 Scott Rickard, <a href="http://costasarrays.org/">costasarrays.org</a> (information and papers about Costas arrays). %Y A213339 Cf. A008404 (Costas arrays), A003319 (connected permutations), A213270 (Costas arrays that are involutions), A213271 (Costas arrays that are derangements), A213338 (Costas arrays that are cyclic). %K A213339 nonn,hard,more %O A213339 1,3 %A A213339 _Joerg Arndt_, Jun 09 2012