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 A233970 #12 Nov 25 2018 12:26:00 %S A233970 0,1,3,5,9,11,15,21,29,31,35,41,51,61,69,83,99,101,105,111,121,131, %T A233970 141,159,183,205,213,227,249,275,291,321,353,355,359,365,375,385,395, %U A233970 413,437,459,469,487,515,553,581,627,683,737,745,759,781,807 %N A233970 Toothpick sequence on hexagonal net starting from the vertex of a 60-degree wedge (see Comments lines for precise definition). %C A233970 Toothpicks are connected by their endpoints. The toothpicks placed in north direction are prohibited. The sequence gives the number of toothpicks after n-th stage in the structure. A233971 (the first differences) give the number of toothpicks added at n-th stage. %C A233970 First differs from A169780 at a(24). %C A233970 First differs from both A233764 and A233780 at a(25). %H A233970 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 A233970 <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a> %Y A233970 Cf. A139250, A161206, A161830, A169780, A182632, A182634, A182634, A182840, A233760, A233764, A233780, A233971, A233972. %K A233970 nonn %O A233970 0,3 %A A233970 _Omar E. Pol_, Dec 18 2013