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A161830 Y-toothpick 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Y-toothpick sequence starting at the corner of an infinite hexagon in which its vertex touch an endpoint of the initial Y-toothpick and the two other endpoints are equidistant from the nearest sides of the hexagon.

The sequence gives the number of Y-toothpicks in the structure after n rounds. A161831 (the first differences) gives the number added at the n-th round.

See the Y-toothpick sequence A160120 for more information about the recursive, fractal-like 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

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

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Last modified February 22 09:44 EST 2018. Contains 299449 sequences. (Running on oeis4.)