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 A160731 #14 Feb 24 2021 02:48:18 %S A160731 2,2,4,6,6,6,12,14,12,6,12,14,16,18,32,34,20,6,12,14,16,18,32,34,24, %T A160731 18,32,38,44,62,92,82,36,6,12,14,16,18,32,34,24,18,32,38,44,62,92,82, %U A160731 40,18,32,38,44,62 %N A160731 First differences of A160730. %H A160731 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 A160731 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> %F A160731 From _Nathaniel Johnston_, Mar 28 2011: (Start) %F A160731 a(n) = 2*A168113(n) %F A160731 a(2^(n+2) + 1) = 4(2^n + 1), n >= 1. %F A160731 (End) %e A160731 Placing the entries starting from a(4) in a triangle with rows that have length equal to powers of two gives: %e A160731 6, 6 %e A160731 6, 12, 14, 12 %e A160731 6, 12, 14, 16, 18, 32, 34, 20 %e A160731 6, 12, 14, 16, 18, 32, 34, 24, 18, 32, 38, 44, 62, 92, 82, 36 %e A160731 ... %e A160731 The rows of this triangle tend to 2*A168114. %Y A160731 Cf. A139250, A139251, A160730, A160733, A160737, A160739, A160741. %K A160731 nonn %O A160731 1,1 %A A160731 _Omar E. Pol_, May 25 2009 %E A160731 Terms after a(11) from _Nathaniel Johnston_, Mar 28 2011