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A274920 Spiral constructed on the nodes of the triangular net in which each new term is the least nonnegative integers distinct from its neighbors. 8
0, 1, 2, 1, 2, 1, 2, 0, 2, 0, 1, 0, 2, 0, 1, 0, 2, 0, 1, 2, 1, 0, 1, 2, 0, 2, 1, 0, 1, 2, 0, 2, 1, 0, 1, 2, 0, 1, 0, 2, 1, 2, 0, 1, 2, 1, 0, 2, 1, 2, 0, 1, 2, 1, 0, 2, 1, 2, 0, 1, 2, 0, 2, 1, 0, 2, 0, 1, 2, 0, 1, 0, 2, 1, 0, 2, 0, 1, 2, 0, 1, 0, 2, 1, 0, 2, 0, 1, 2, 0, 1, 2, 1, 0, 2, 1, 0, 1, 2, 0, 1, 2, 0, 2, 1, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
The structure of the spiral has the following properties:
1) Positive terms are on the nodes of a hexagonal net.
2) Every 0 is surrounded by three equidistant 1's and three equidistant 2's.
3) Every 1 is surrounded by three equidistant 0's and three equidistant 2's.
4) Every 2 is surrounded by three equidistant 0's and three equidistant 1's.
5) Diagonals are periodic sequences with period 3 (A010872 and A080425).
For the connection with the structure of graphene see also A275606.
LINKS
FORMULA
a(n) = A274921(n) - 1.
EXAMPLE
Illustration of initial terms as a spiral:
.
. 2 - 0 - 1 - 2 - 0 - 1
. / \
. 0 1 - 2 - 0 - 1 - 2 0
. / / \ \
. 1 2 0 - 1 - 2 - 0 1 2
. / / / \ \ \
. 2 0 1 2 - 0 - 1 2 0 1
. / / / / \ \ \ \
. 0 1 2 0 1 - 2 0 1 2 0
. / / / / / \ \ \ \ \
. 1 2 0 1 2 0 - 1 2 0 1 2
. \ \ \ \ \ / / / /
. 0 1 2 0 1 - 2 - 0 1 2 0
. \ \ \ \ / / /
. 2 0 1 2 - 0 - 1 - 2 0 1
. \ \ \ / /
. 1 2 0 - 1 - 2 - 0 - 1 2
. \ \ /
. 0 1 - 2 - 0 - 1 - 2 - 0
. \
. 2 - 0 - 1 - 2 - 0 - 1
.
CROSSREFS
Sequence in context: A060024 A143668 A029445 * A316828 A350223 A274820
KEYWORD
nonn
AUTHOR
Omar E. Pol, Jul 11 2016
STATUS
approved

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Last modified April 16 04:17 EDT 2024. Contains 371696 sequences. (Running on oeis4.)