A160123 - OEIS

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A160123

a(n) = A160121(n+1)/3.

1, 1, 3, 1, 3, 3, 7, 3, 3, 3, 7, 5, 7, 9, 17, 9, 3, 3, 7, 5, 7, 9, 17, 11, 7, 9, 17, 17, 19, 23, 39, 27, 7, 3, 7, 5, 7, 9, 17, 11, 7, 9, 17, 17, 19, 23, 39, 29, 11, 9, 17, 17, 19, 25, 43, 39, 25, 23, 39, 45, 47, 57, 93, 77, 23, 3, 7, 5, 7, 9

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OFFSET

1,3

COMMENTS

Also, first differences of A161910. [From Omar E. Pol, Jun 21 2009]

LINKS

Table of n, a(n) for n=1..70.

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

EXAMPLE

Note that this can be written as a triangle:

1,3;

3,7,3,3;

3,7,5,7,9,17,9,3;

3,7,5,7,9,17,11,7,9,17,17,19,23,39,27,7;

3,7,5,7,9,17,11,7,9,17,17,19,23,39,29,11,9,17,17,19,25,43,39,25,23,39,45,47,57,93,77,23;

3,7,5,7,9,...

CROSSREFS

Y-toothpick sequence: A160120. Cf. A160121, A160122.

Cf. A139250, A139251. [From Omar E. Pol, Jun 16 2009]