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 A172309 #12 Feb 24 2021 02:48:19 %S A172309 0,1,2,2,2,4,4,2,4,6,6,8,6,12,10,6,4,6,10,12,10,14,14,16,16,18,14,16, %T A172309 12,20,22,8,8,16,18,16,10,16,20,24,26,36,24,32,30,40,28,24 %N A172309 Number of L-toothpicks added to the L-toothpick structure of A172308 (First quadrant) at the n-th stage. %H A172309 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 A172309 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> %F A172309 a(0) = 0, a(n) = A172305(n+1)/4, for n>=1. %Y A172309 Cf. First differences of A172308. %Y A172309 Cf. A139250, A139251, A152978, A172304, A172305, A172306, A172307, A172308, A172310, A172311, A172312, A172313. %K A172309 more,nonn %O A172309 0,3 %A A172309 _Omar E. Pol_, Feb 06 2010 %E A172309 More terms from _Colin Barker_, Apr 19 2015