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 A294981 #16 Feb 04 2019 14:00:43 %S A294981 1,3,6,6,6,18,18,18,6 %N A294981 a(n) is the number of elements added at n-th stage to the structure of the cellular automaton of A294980. %H A294981 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 A294981 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a> %H A294981 <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a> %e A294981 This cellular automaton has word "ab". The row lengths are the terms of A011782 multiplied by 2, so the structure of this irregular triangle is as follows: %e A294981 a,b; %e A294981 a,b; %e A294981 a,b,a,b; %e A294981 a,b,a,b,a,b,a,b; %e A294981 a,b,a,b,a,b,a,b,a,b,a,b,a,b,a,b; %e A294981 ... %e A294981 Triangle begins: %e A294981 1, 3; %e A294981 6, 6; %e A294981 6, 18, 18, 18; %e A294981 ... %Y A294981 Cf. A294980, A296612 (gives more information about the "word" of a cellular automaton). %Y A294981 Cf. A139251, A160121 (Y-toothpicks), A161207 (V-toothpicks). %K A294981 nonn,tabf,more %O A294981 1,2 %A A294981 _Omar E. Pol_, Feb 10 2018