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 A274702 #31 Jul 08 2016 00:17:08 %S A274702 1,2,6,47 %N A274702 a(n) = number of arrangements of n circles in the affine plane in which all circles share part of their boundary with the boundary of the union of all the circles. %C A274702 Consider the arrangements of n circles described in A250001. %Y A274702 Leading diagonal of triangle A249752. %Y A274702 Cf. A250001. %K A274702 nonn,hard,more %O A274702 1,2 %A A274702 _Omar E. Pol_, Jul 06 2016