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 A288561 #14 Jul 09 2025 04:44:14 %S A288561 1,1,6,112,15528 %N A288561 Number of connected arrangements of n pseudo-circles in the affine plane, in the sense that the union of the boundaries of the pseudo-circles is a connected set. %C A288561 Arrangements in A288559 that are connected, in the sense that the union of the (boundaries of the) pseudo-circles is a connected set. %C A288561 These counts have been reduced for mirror symmetry. %C A288561 See A250001, the main entry for this problem, for further information. %Y A288561 Cf. A250001, A275923, A275924, A288554-A288568. %K A288561 nonn,more %O A288561 0,3 %A A288561 _N. J. A. Sloane_, Jun 13 2017, based on information supplied by _Jon Wild_ on Aug 31 2016