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 A161417 #6 Feb 24 2021 02:48:18 %S A161417 1,7,3,21,7,41,9,57,13 %N A161417 First differences of A160416. %H A161417 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 A161417 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 A161417 Cf. A139250, A139251, A153006, A152980, A160411, A160413, A160415, A160416. %Y A161417 Cf. A160797. %K A161417 more,nonn %O A161417 1,2 %A A161417 _Omar E. Pol_, May 20 2009, Jun 14 2009