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 A161910 Y-toothpick sequence starting at the corner of an infinite hexagon from which protudes a half toothpick with an angle = Pi/6. 1
 0, 1, 2, 5, 6, 9, 12, 19, 22, 25, 28, 35, 40, 47, 56, 73 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS The sequence gives the number of Y-toothpicks in the structure after n rounds. A160123 (the first differences) gives the number added at the n-th round. See the entries A160120, A161830 and A161426 for more information about Y-toothpick sequences. LINKS David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, 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.] N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS FORMULA a(n) = (A160120(n+1)-1)/3. CROSSREFS Cf. A160120, A160121, A160123, A160406, A161830, A161831. Sequence in context: A046962 A022486 A267700 * A151920 A160714 A256644 Adjacent sequences:  A161907 A161908 A161909 * A161911 A161912 A161913 KEYWORD more,nonn AUTHOR Omar E. Pol, Jun 21 2009 STATUS approved

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Last modified September 20 19:05 EDT 2019. Contains 327246 sequences. (Running on oeis4.)