%I #8 Feb 24 2021 02:48:18
%S 0,1,4,7,14,19,26,35,52,63,70
%N Y-toothpick sequence starting at the outside corner of an infinite triangle-shaped polygon as the sieve of A160120 after 2^k rounds.
%C The sequence gives the number of Y-toothpicks after n rounds. A161427 (the first differences) gives the number added at the n-th round.
%C See the entries A160120, A139250 and A153006 for more information.
%H 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 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>
%H David Applegate, <a href="/A139250/a139250.anim.html">The movie version</a>
%Y Cf. A000079, A139250, A153006, A160120, A161427, A161830.
%K more,nonn
%O 0,3
%A _Omar E. Pol_ and _David Applegate_, Jun 20 2009