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 A287149 #37 Feb 13 2018 09:14:05 %S A287149 1,1,2,11,155 %N A287149 Number of arrangements of n circles in the affine plane having only one island or region, which is formed by the union of all solid circles of the arrangement. %C A287149 A subset of the arrangements of n circles described in A250001. %C A287149 Note that a(4) = 155 does not include the arrangement of four circles in which there is a little circle that is surrounded by the union of three solid circles, because in that arrangement there are two islands or regions, not one. %Y A287149 1 together with the first column of A252158. %Y A287149 First differs from A275923 at a(4). %Y A287149 Cf. A250001. %K A287149 nonn,hard,more %O A287149 0,3 %A A287149 _Omar E. Pol_, May 21 2017