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%I #6 Feb 24 2021 02:48:18
%S 0,1,2,4,5,7,9,13,15,17,19,23,26,30,35,44,49,51
%N a(n) = (A161830(n+1)-1)/2.
%C The sequence gives the number of Y-toothpicks in the structure after n rounds. A161833 (the first differences) gives the number added at the n-th round.
%C See the Y-toothpick sequence A160120 and A161830 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>
%Y Cf. A139250, A160120, A160406, A161830, A161831, A161833.
%K more,nonn
%O 0,3
%A _Omar E. Pol_, Jun 20 2009