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A161210
Toothpick sequence starting at the outside corner of an infinite cube from which protrudes a half toothpick.
4
0, 1, 3, 7, 14, 21, 28
OFFSET
0,3
COMMENTS
The sequence gives the number of toothpicks after n rounds. A161211 (the first differences) gives the number added at the n-th round.
This structure is a three-dimensional version of the toothpick structure of A153006.
Toothpicks are placed following a rotation of axes: x,y,z,x,y,z,... and so on.
See A139250 and A160160 for more information about the toothpick sequences.
LINKS
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.]
KEYWORD
more,nonn
AUTHOR
Omar E. Pol, Jun 06 2009
STATUS
approved