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A160173 Number of T-toothpicks added at n-th stage to the T-toothpick structure of A160172. 16
0, 1, 3, 5, 9, 9, 9, 13, 25, 21, 9, 13, 25, 25, 25, 37, 73, 57, 9, 13, 25, 25, 25, 37, 73, 61, 25, 37, 73, 73, 73, 109, 217, 165, 9, 13, 25, 25, 25, 37, 73, 61, 25, 37, 73, 73, 73, 109, 217, 169, 25, 37, 73, 73, 73, 109, 217, 181, 73, 109, 217, 217, 217, 325, 649, 489, 9, 13, 25 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Essentially the first differences of A160172.

For further information see the Applegate-Pol-Sloane paper, chapter 11: T-shaped toothpicks. See also the figure 16 in the mentioned paper. - Omar E. Pol, Nov 18 2011

The numbers n in increasing order such that the triple [n, n, n] can be found here, give A199111. [Observed by Omar E. Pol, Nov 18 2011. Confirmed by Alois P. Heinz, Nov 21 2011]

REFERENCES

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

LINKS

Table of n, a(n) for n=0..68.

David Applegate, The movie version

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.], which is also available at arXiv:1004.3036v2

N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS

Index entries for sequences related to toothpick sequences

FORMULA

a(n) = (2/3)*(3^wt(n-1) + 3^wt(n-2))+1 (where wt is A000120), for n >= 3. - N. J. A. Sloane, Jan 01 2010

EXAMPLE

From Omar E. Pol, Feb 09 2010: (Start)

If written as a triangle:

0;

1;

3;

5;

9,9;

9,13,25,21;

9,13,25,25,25,37,73,57;

9,13,25,25,25,37,73,61,25,37,73,73,73,109,217,165;

9,13,25,25,25,37,73,61,25,37,73,73,73,109,217,169,25,37,73,73,73,109,217,181,73,109,217,217,217,325,649,489;

9,13,25,25,25,37,73,61,25,37,73,73,73,109,217,169,25,37,73,73,73,109...

(End)

MATHEMATICA

wt[n_] := DigitCount[n, 2, 1];

a[0] = 0; a[1] = 1; a[2] = 3; a[n_] := 2/3 (3^wt[n-1] + 3^wt[n-2]) + 1;

Table[a[n], {n, 0, 68}] (* Jean-Fran├žois Alcover, Aug 18 2018, after N. J. A. Sloane *)

CROSSREFS

Cf. A139250, A139251, A160172, A160121, A160171, A161207, A161329, A172311.

Sequence in context: A254689 A176445 A292863 * A256537 A092996 A141264

Adjacent sequences:  A160170 A160171 A160172 * A160174 A160175 A160176

KEYWORD

nonn

AUTHOR

Omar E. Pol, Jun 01 2009

EXTENSIONS

More terms from N. J. A. Sloane, Jan 01 2010

STATUS

approved

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Last modified December 11 07:18 EST 2019. Contains 329914 sequences. (Running on oeis4.)