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 A161831 #6 Feb 24 2021 02:48:18 %S A161831 1,2,2,4,2,4,4,8,4,4,4,8,6,8,10,18,10,4 %N A161831 First differences of A161830. %C A161831 Number of Y-toothpicks added to the sieve at the n-th round. %H A161831 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 A161831 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 A161831 Cf. A139250, A139251, A160121, A160407, A161830, A161832, A161833. %K A161831 more,nonn %O A161831 1,2 %A A161831 _Omar E. Pol_, Jun 20 2009