%N Number of segments needed to draw the toothpick structure of A139250 as it is after n stages.
%C Contribution from _Omar E. Pol_, Sep 16 2012 (Start):
%C It appears that A147614(n)/a(n) converge to 4.
%C It appears that A139250(n)/a(n) converge to 3.
%C It appears that A160124(n)/a(n) converge to 2.
%H Nathaniel Johnston, <a href="/A139252/b139252.txt">Table of n, a(n) for n = 0..256</a>
%H David Applegate, Omar E. Pol and N. J. A. Sloane, <a href="http://neilsloane.com/doc/tooth.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 Nathaniel Johnston, <a href="/A139252/a139252.c.txt">C script for computing table of terms</a>
%H 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 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 Cf. A139250, A139251, A139253, A147614, A160124, A139254, A139255, A160128.
%A _Omar E. Pol_, May 17 2008
%E Terms after a(28) from _Nathaniel Johnston_, Mar 29 2011