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 A160809 #10 Feb 24 2021 02:48:18 %S A160809 1,2,4,4,4,8,12,4,1,2,3,3,4,7,8,1,2,3,3,4,5,7,5,3,5,7,8,11,13,17,12,4, %T A160809 5,8,7,9,5,7,9,8,4,8,8,7,8,13,14,10,8,12,11,13,13,17,16,11,8,15,13,14, %U A160809 19,26,21,5,7 %N A160809 First differences of A160808. %C A160809 Number of toothpicks added to the spiral at the n-th stage. %H A160809 Nathaniel Johnston, <a href="/A160809/b160809.txt">Table of n, a(n) for n = 1..254</a> %H A160809 David Applegate, Omar E. Pol and N. J. A. Sloane, <a href="/A000695/a000695_1.pdf">The Toothpick Sequence and Other Sequences from Cellular Automata</a>, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.] %H A160809 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> %Y A160809 Cf. A000045, A139250, A139251, A160426, A160427, A160800, A160801, A160802, A160803, A160808. %K A160809 nonn %O A160809 1,2 %A A160809 _Omar E. Pol_, May 26 2009 %E A160809 Terms after a(16) from _Nathaniel Johnston_, Mar 30 2011