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 A170884 #15 Feb 24 2021 02:48:19 %S A170884 0,3,7,15,27,39,51,67,99,155,223,263,283,299,331,387,467,555,659,811, %T A170884 1067,1443,1831,1995,2059,2083,2123,2179,2259,2347,2451,2603,2859, %U A170884 3235,3659,3955,4211,4483,4899,5451 %N A170884 In the toothpick structure of A160160, the number of nodes occupied after n steps, assuming that the toothpicks have length 2. %C A170884 See A170885 for the first differences. %H A170884 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 A170884 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 A170884 Cf. A139250, A170885. %K A170884 nonn %O A170884 0,2 %A A170884 _David Applegate_, _Omar E. Pol_ and _N. J. A. Sloane_, Jan 09 2010 %E A170884 a(7)-a(39) from _Nathaniel Johnston_, Nov 13 2010