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 A273280 #9 Mar 24 2017 00:47:59 %S A273280 1,1,2,5,19,129,1806 %N A273280 Number of topologically-distinct slicings of a square by n lines in general position. %C A273280 Similar to A272906, but for squares instead of circles. Here a square is cut by a set of n lines in general position, i.e., there are no parallel lines nor 3 lines concurrent in a point. For every slicing we build a graph which has one node per region and an edge between two nodes if the corresponding regions are adjacent. This sequence gives the number of distinct graphs up to isomorphism. See illustration in Links. %C A273280 Current terms have been obtained by generating about 10^8 randomized slicings: it would be better to confirm these values by means of a systematic enumeration. %C A273280 This sequence differs from A272906 starting from a(5). Indeed, in the circle, the slicing produced by 5 chords arranged like an inscribed pentagon corresponds to a 5-star graph, which is impossible to attain in the square, since there are only 4 corners the lines can cut. %H A273280 Giovanni Resta, <a href="/A273280/a273280.pdf">Illustration of a(3)-a(5)</a> %Y A273280 Cf. A272906, A090338. %K A273280 nonn,more %O A273280 0,3 %A A273280 _Giovanni Resta_, May 19 2016