A160808 Toothpick sequence in Fibonacci spiral (see Comments lines for definition).

0, 1, 3, 7, 11, 15, 23, 35, 39, 40, 42, 45, 48, 52, 59, 67, 68, 70, 73, 76, 80, 85, 92, 97, 100, 105, 112, 120, 131, 144, 161, 173, 177, 182, 190, 197, 206, 211, 218, 227, 235, 239, 247, 255, 262, 270, 283, 297

Offset: 0

Author

Omar E. Pol, May 26 2009

Keywords

• nonn

Comments

On the infinite square grid we draw a Fibonacci spiral starting with 4,4,8,12,20,32,... (Note that each edge has length = A000045(k)*4, for k>0). We start at stage 0 with no toothpicks. At stage 1 we place a toothpick of length 2 in a orthogonal direction, in the center of the Fibonacci spiral. At stage 2 we place 2 toothpicks. And so on... The sequence gives the number of toothpicks in the Fibonacci spiral after n stages. A160809 (the first differences) gives the number added at the n-th stage. See 160800, A160802 and A139250 for more information about toothpick sequences.

Links

• Nathaniel Johnston, Table of n, a(n) for n = 0..256
• 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
• Nathaniel Johnston, C script for computing terms

Crossrefs

Cf. A000045, A139250, A139251, A160426, A160427, A160800, A160801, A160802, A160803, A160809.

Extensions

Terms after a(16) from Nathaniel Johnston, Mar 30 2011