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A160406
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Toothpick sequence starting at the vertex of an infinite 90-degree wedge.
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32
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0, 1, 2, 4, 6, 8, 10, 14, 18, 20, 22, 26, 30, 34, 40, 50, 58, 60, 62, 66, 70, 74, 80, 90, 98, 102, 108, 118, 128, 140, 160, 186, 202, 204, 206, 210, 214, 218, 224, 234, 242, 246, 252, 262, 272, 284, 304, 330, 346, 350, 356, 366, 376, 388, 408, 434, 452, 464, 484, 512, 542, 584
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OFFSET
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0,3
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COMMENTS
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Consider the wedge of the plane defined by points (x,y) with y >= |x|, with the initial toothpick extending from (0,0) to (0,2); then extend by the same rule as for A139250, always staying inside the wedge.
Number of toothpick in the structure after n rounds.
The toothpick sequence A139250 is the main entry for this sequence. See also A153000. First differences: A160407.
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LINKS
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Table of n, a(n) for n=0..61.
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
Omar Pol, Illustration of initial terms
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FORMULA
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A139250(n) = 2a(n) + 2a(n+1) - 4n - 1 for n>0. - N. J. A. Sloane, May 25 2009
Let G = (x + 2*x^2 + 4*x^2*(1+x)*(mul(1+x^(2^k-1)+2*x^(2^k),k=1..oo)-1)/(1+2*x))/(1-x) (= g.f. for A139250); then the g.f. for the present sequence is (G + 2 + x*(5-x)/(1-x)^2)*x/(2*(1+x)). - N. J. A. Sloane, May 25 2009
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MAPLE
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G := (x + 2*x^2 + 4*x^2*(1+x)*(mul(1+x^(2^k-1)+2*x^(2^k), k=1..20)-1)/(1+2*x))/(1-x); P:=(G + 2 + x*(5-x)/(1-x)^2)*x/(2*(1+x)); series(P, x, 200); seriestolist(%); - N. J. A. Sloane, May 25 2009
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CROSSREFS
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Cf. A139250, A139251, A153000, A153006, A152980, A160407, A160408, A160409.
Cf. A170886-A170895.
Sequence in context: A191146 A220850 A151566 * A113293 A080431 A288732
Adjacent sequences: A160403 A160404 A160405 * A160407 A160408 A160409
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KEYWORD
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nonn
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AUTHOR
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Omar E. Pol, May 23 2009
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EXTENSIONS
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More terms from N. J. A. Sloane, May 25 2009
Definition revised by N. J. A. Sloane, Jan 02 2010
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STATUS
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approved
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