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 A160724 #12 Feb 24 2021 02:48:18 %S A160724 0,3,6,15,18,27,36,63,66,75,84,111,120,147,174,255,336,339 %N A160724 a(n) = A160714(n)*3. %C A160724 The sequence gives the number of T-toothpicks in the structure after n rounds. %C A160724 See A160172 and A160714 for more information about T-toothpick sequences. %H A160724 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 A160724 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 A160724 Cf. A139250, A160172, A160173, A160714, A160726. %K A160724 nonn,more %O A160724 0,2 %A A160724 _Omar E. Pol_, Jun 02 2009 %E A160724 a(9)-a(17) from 3*A160714(n) by _Jinyuan Wang_, Mar 14 2020