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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 Table of n, a(n) for n=0..105. 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 Cf. A010872, A080425, A274820, A274821, A274921, A275606, A275610. Sequence in context: A060024 A143668 A029445 * A316828 A350223 A274820 Adjacent sequences: A274917 A274918 A274919 * A274921 A274922 A274923 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.)