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 A210985 #18 Jan 21 2016 16:38:05 %S A210985 1,3,7,19,63,235,919,3651,14575 %N A210985 Number of segments needed to draw the toothpick structure of A139250 as it is after 2^n stages. %C A210985 It appears that this is also the partial sums of A039301. %C A210985 It appears that this is also 1 together with A160128. %H A210985 David Applegate, <a href="/A139250/a139250.anim.html">The movie version</a> %H A210985 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 A210985 a(n) = A139252(2^n). %e A210985 For n = 3, after 2^3 stages the toothpick structure of A139250 contains 43 toothpicks (A139250(2^3) = 43). However the toothpick structure can be essentially represented by 19 segments (A139252(2^3) = 19), so a(3) = 19. %Y A210985 Cf. A007583, A039301, A139250, A139252, A147614, A160128. %K A210985 nonn,more %O A210985 0,2 %A A210985 _Omar E. Pol_, Sep 11 2012