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A272573 Start a spiral of numbers on a hexagonal tiling, with the initial hexagon as a(1) = 1. a(n) is the smallest positive integer not equal to or previously adjacent to its neighbors. 2
1, 2, 3, 4, 5, 6, 7, 4, 6, 8, 5, 9, 8, 10, 2, 11, 3, 10, 11, 12, 13, 9, 12, 7, 13, 14, 1, 11, 13, 15, 9, 16, 14, 7, 16, 17, 15, 1, 16, 18, 7, 17, 19, 20, 1, 17, 18, 19, 9, 21, 3, 20, 10, 22, 4, 15, 21, 23, 5, 22, 23, 10, 21, 6, 22, 24, 25, 2, 14, 22, 25, 26, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This is the hexagonal analog to A260643.

LINKS

Peter Kagey, Table of n, a(n) for n = 1..10000

Peter Kagey, Ruby program for computing sequence.

EXAMPLE

Illustration of a(1) through a(8) and a(13):

    |     |     |      |       |       |       |        |     | 8 9 5

    |     |  3  | 4 3  |  4 3  |  4 3  |  4 3  |  4 3   |     |  4 3 8

  1 | 1 2 | 1 2 |  1 2 | 5 1 2 | 5 1 2 | 5 1 2 | 5 1 2  | ... | 5 1 2 6

    |     |     |      |       |  6    |  6 7  |  6 7 4 |     |  6 7 4

CROSSREFS

Cf. A047932, A260643.

Sequence in context: A115871 A138221 A038388 * A319999 A083501 A007922

Adjacent sequences:  A272570 A272571 A272572 * A272574 A272575 A272576

KEYWORD

nonn

AUTHOR

Peter Kagey, May 03 2016

STATUS

approved

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Last modified March 23 05:36 EDT 2019. Contains 321422 sequences. (Running on oeis4.)