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 A139252 #20 Feb 24 2021 02:48:18 %S A139252 0,1,3,5,7,11,15,17,19,23,27,31,39,51,59,61,63,67,71,75,83,95,103,107, %T A139252 115,127,139,155,183,215,231,233,235,239,243,247,255,267,275,279,287, %U A139252 299,311,327,355,387,403,407,415 %N A139252 Number of segments needed to draw the toothpick structure of A139250 as it is after n stages. %C A139252 Contribution from _Omar E. Pol_, Sep 16 2012 (Start): %C A139252 It appears that A147614(n)/a(n) converge to 4. %C A139252 It appears that A139250(n)/a(n) converge to 3. %C A139252 It appears that A160124(n)/a(n) converge to 2. %C A139252 (End) %H A139252 Nathaniel Johnston, <a href="/A139252/b139252.txt">Table of n, a(n) for n = 0..256</a> %H A139252 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 A139252 Nathaniel Johnston, <a href="/A139252/a139252.c.txt">C script for computing table of terms</a> %H A139252 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> %e A139252 For n = 3, after three stages the toothpick structure of A139250 contains seven toothpicks (A139250(3) = 7), however the toothpick structure can be essentially represented by five segments, so a(3) = 5. - _Omar E. Pol_, Sep 16 2012 %Y A139252 Cf. A139250, A139251, A139253, A147614, A160124, A139254, A139255, A160128. %K A139252 nonn %O A139252 0,3 %A A139252 _Omar E. Pol_, May 17 2008 %E A139252 Terms after a(28) from _Nathaniel Johnston_, Mar 29 2011