

A161830


Ytoothpick triangle (see Comments lines for definition).


9



0, 1, 3, 5, 9, 11, 15, 19, 27, 31, 35, 39, 47, 53, 61, 71, 89, 99, 103
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OFFSET

0,3


COMMENTS

Ytoothpick sequence starting at the corner of an infinite hexagon in which its vertex touch an endpoint of the initial Ytoothpick and the two other endpoints are equidistant from the nearest sides of the hexagon.
The sequence gives the number of Ytoothpicks in the structure after n rounds. A161831 (the first differences) gives the number added at the nth round.
See the Ytoothpick sequence A160120 for more information about the recursive, fractallike structure.


LINKS

Table of n, a(n) for n=0..18.
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n1)1) for n >= 2.]
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS


CROSSREFS

Cf. A139250, A160120, A160121, A160406, A160407, A161831, A161832, A161833.
Sequence in context: A216091 A002731 A006046 * A151922 A233762 A104635
Adjacent sequences: A161827 A161828 A161829 * A161831 A161832 A161833


KEYWORD

more,nonn


AUTHOR

Omar E. Pol, Jun 20 2009


STATUS

approved



