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 A261409 #13 Aug 27 2015 11:50:51 %S A261409 -11,21,25,27,28,34,36,40,42,43,46,48,49,51,54,57,61,63,64,67,69,70, %T A261409 72,73,75,78,79,81,82,84,85 %N A261409 Curvatures in a certain bounded, integral, primitive Soddy sphere packing. %C A261409 A three-dimensional Apollonian packing. %H A261409 Nicolas Hannachi, <a href="/A261409/a261409.png">Illustration of this packing, showing some of the initial terms</a> [Fig. 2b in Kontorovich (2012), used with permission] %H A261409 Nicolas Hannachi, <a href="http://maths.ac-noumea.nc/polyhedr/packing.htm">Des cercles tangents et des sphères tangentes</a> %H A261409 Alex Kontorovich, <a href="http://arxiv.org/abs/1208.5441">The local-global principle for integral Soddy sphere packings</a>, arXiv:1208.5441, 2012. %Y A261409 Cf. A261410. %K A261409 sign,more %O A261409 1,1 %A A261409 _N. J. A. Sloane_, Aug 23 2015