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 A194700 #20 Jan 30 2016 18:48:22 %S A194700 0,1,5,13,29,51,75,97,137,177,209,241,297,371,467,533 %N A194700 D-toothpick sequence of the third kind (see Comments lines for definition). %C A194700 This is a cellular automaton of forking paths to 135 degrees which uses elements of three sizes: toothpicks of length 1, D-toothpicks of length 2^(1/2) and D-toothpicks of length 2^(1/2)/2. Toothpicks are placed in horizontal or vertical direction. D-toothpicks are placed in diagonal direction. Toothpicks and D-toothpicks are connected by their endpoints. %C A194700 On the infinite square grid we start with no elements. %C A194700 At stage 1, place a single D-toothpick on the paper, in diagonal direction. %C A194700 The rule for adding new elements is as follows. Each exposed endpoint of the elements of the old generation must be touched by the two endpoints of two elements of the new generation such that the angle between the old element and each new element is equal to 135 degrees. Intersections and overlapping are prohibited. %C A194700 This toothpick structure is very similar to A194270, but here there are no toothpicks endpoints that remain exposed forever. %H A194700 David Applegate, <a href="/A139250/a139250.anim.html">The movie version</a> %H A194700 N. J. A. Sloane, <a href="/wiki/Catalog_of_Toothpick_and_CA_Sequences_in_OEIS">Catalog of Toothpick and Cellular Automata Sequences in the OEIS</a> %H A194700 <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a> %Y A194700 Cf. A139250, A194270. %K A194700 nonn,more %O A194700 0,3 %A A194700 _Omar E. Pol_, Sep 02 2011