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 A229757 #14 Jul 14 2019 05:24:28 %S A229757 1,2,3,4,5,7,8,9,11,12,15,17,20,21,23,29,36,39,41,44,84 %N A229757 Numbers n such that no convex hexagon exists that can be dissected into n congruent equilateral triangles. %C A229757 Numbers not expressible as k = 2*(a*c + b*c + b*d) - (a-d)^2 with a,b,c,d >= 1, a < c+d, d < a+b. %C A229757 See the Hertel paper for the finiteness proof. %H A229757 Eike Hertel, <a href="http://www.minet.uni-jena.de/preprints/hertel_13/Regdreipfla.pdf">Reguläre Dreieckspflasterungen konvexer Polygone</a>, Jenaer Schriften zur Mathematik und Informatik, Math/Inf/01/13, 2013 (preprint). %H A229757 Eike Hertel, Christian Richter, <a href="https://doi.org/10.1007/s00454-014-9576-7">Tiling Convex Polygons with Congruent Equilateral Triangles</a>, Discrete Comput Geom (2014) 51:753-759. %H A229757 Kival Ngaokrajang, <a href="/A229757/a229757.pdf">Illustration of initial terms</a> %Y A229757 Cf. A229461 (Pentagon exception numbers). %K A229757 nonn,fini,full %O A229757 1,2 %A A229757 Suggested by Eike Hertel, _Hugo Pfoertner_, Sep 28 2013