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 A178573 #23 Jul 20 2019 14:22:32 %S A178573 2,4,8,8,8,12,20,16,8,12,24,32,28,28,44,32,8,12,24,32,32,40,64,72,44, %T A178573 28,56,84,80,72,100,64,8,12,24,32,32,40,64,72,48,40,72,112,120,112, %U A178573 144,152,76,28,56,84 %N A178573 Number of exposed endpoints in the toothpick structure of A182840. %H A178573 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 A178573 Olaf Voß, <a href="/wiki/Toothpick_structures_on_hexagonal_net">Toothpick structures on hexagonal net</a> %H A178573 <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a> %e A178573 At stage 1 we place a toothpick anywhere in the plane (for example, in vertical position). There are two exposed endpoints, so a(1)=2. %e A178573 At stage 2 we place 4 toothpicks: two new toothpicks touching each exposed endpoint. There are now 4 exposed endpoints, so a(2)=4. %K A178573 nonn %O A178573 1,1 %A A178573 _Olaf Voß_, Dec 24 2010