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 A173458 #13 Feb 24 2021 02:48:19 %S A173458 4,6,2,14,18,2,14,18,6,42,54,2,14,18,6,42,54,6,42,54,18,126,162,2,14, %T A173458 18,6,42,54,6,42,54,18,126,162,6,42,54,18,126,162,18,126,162,54,378, %U A173458 486,2,14,18,6,42,54,6,42,54,18,126,162,6,42,54,18,126,162 %N A173458 a(n) = A173457(n+1)/2. %H A173458 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 A173458 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> %e A173458 From Omar E. Pol, Apr 22 2013 (Start): %e A173458 When written as an irregular triangle begins: %e A173458 4,6; %e A173458 2,14,18; %e A173458 2,14,18,6,42,54; %e A173458 2,14,18,6,42,54,6,42,54,18,126,162; %e A173458 2,14,18,6,42,54,6,42,54,18,126,162,6,42,54,18,126,162,18, 126,162,54,378,486; %e A173458 2,14,18,6,42,54,6,42,54,18,126,162,6,42,54,18,126,162,... %e A173458 (End) %Y A173458 Cf. A173456, A173457, A173459, A173462. %K A173458 nonn,tabf %O A173458 1,1 %A A173458 _Omar E. Pol_, Feb 18 2010 %E A173458 a(13)-a(65) from _Lars Blomberg_, Apr 22 2013