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 A299478 #14 Feb 04 2019 14:02:48 %S A299478 0,1,3,7,13,21,27,33,43,59,79,91,101,117,137,169,193,215,249,285,325, %T A299478 341,355,375,399,439,471,503,547,595,659,707,749,807,877,981,1055, %U A299478 1115,1193,1271,1351,1375,1389,1409,1433,1473,1509,1549,1599,1651,1723 %N A299478 Toothpick sequence on triangular grid with word "abcbc". %C A299478 a(n) gives the number of toothpicks of length 2 in the structure after n-th stage. %C A299478 A299479 (the first differences) gives the number of toothpicks added at n-th stage. %C A299478 For more information about the "word" of a cellular automaton see A296612. %H A299478 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 A299478 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a> %H A299478 <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a> %Y A299478 Cf. A299479 (first differences). %Y A299478 Cf. A160120 (word "a"), A139250 (word "ab"), A296510 (word "abc"), A299476 (word "abcb"). %K A299478 nonn,more %O A299478 0,3 %A A299478 _Omar E. Pol_, Feb 11 2018