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 A121604 #4 Aug 13 2020 14:25:50 %S A121604 2,3,4,5,6,6,7,8,9 %N A121604 Numbers k such that the radius of the smallest circle into which A121603(m) unit circles can be packed is 1 + csc(Pi/k). %C A121604 From the diagrams in the link it appears likely that 10,12,12 are the next three terms. %H A121604 E. Friedman, <a href="https://erich-friedman.github.io/packing/cirincir/">Erich's Packing Center: "Circles in Circles"</a> %e A121604 See A121602 for the case a(8) = 9 pertaining to A121603(8) = 11 unit circles. %Y A121604 Cf. A121603, A121570, A121598, A121601, A121602. %K A121604 nonn %O A121604 0,1 %A A121604 _Rick L. Shepherd_, Aug 09 2006