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 A183149 #13 Feb 24 2021 02:48:19 %S A183149 0,1,3,9,9,21,9,21,21,57,9,21,21,57,21,57,57,165,9,21,21,57,21,57,57, %T A183149 165,21,57,57,165,57,165,165,489,9,21,21,57,21,57,57,165,21,57,57,165, %U A183149 57,165,165,489,21,57,57,165,57,165 %N A183149 Number of toothpicks added at n-th stage to the toothpick structure of A183148. %C A183149 Essentially the first differences of A183148. %H A183149 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 A183149 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 A183149 a(n) = 3*A183061(n-1), for n >=2 %e A183149 If written as a triangle begins: %e A183149 0, %e A183149 1, %e A183149 3, %e A183149 9, %e A183149 9,21, %e A183149 9,21,21,57, %e A183149 9,21,21,57,21,57,57,165, %e A183149 9,21,21,57,21,57,57,165,21,57,57,165,57,165,165,489, %Y A183149 Cf. A139250, A139251, A147582, A147610, A160173, A161411, A183061, A183127, A183148. %K A183149 nonn %O A183149 0,3 %A A183149 _Omar E. Pol_, Mar 28 2011, Apr 02 2011