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 A187217 #18 Feb 24 2021 02:48:19 %S A187217 0,2,6,8,14,22,30,22,38,54,70,22,38,54,70,54,102,150,134,22,38,54,70, %T A187217 54,102,150,134,54,102,150,166,182,326,406,262,22,38,54,70,54,102,150, %U A187217 134,54,102,150,166,182,326,406,262,54,102,150,166,182,326,406,294,182,326 %N A187217 Number of Q-toothpicks added at n-th stage to the structure of A187216. %C A187217 Essentially the first differences of A187216. %H A187217 Nathaniel Johnston, <a href="/A187217/b187217.txt">Table of n, a(n) for n = 0..200</a> %H A187217 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 A187217 Nathaniel Johnston, <a href="http://www.nathanieljohnston.com/2011/03/the-q-toothpick-cellular-automaton/">The Q-Toothpick Cellular Automaton</a> %H A187217 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> %Y A187217 Cf. A139250, A139251, A187216, A187211, A187213, A187221. %K A187217 nonn %O A187217 0,2 %A A187217 _Omar E. Pol_, Mar 30 2011 %E A187217 a(15) - a(60) from _Nathaniel Johnston_, Apr 15 2011