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A068226
Neighbor in 2-1 direction of numbers arranged as clockwise spiral.
5
6, 1, 4, 5, 18, 19, 20, 7, 8, 9, 2, 3, 14, 15, 16, 17, 38, 39, 40, 41, 42, 21, 22, 23, 24, 25, 10, 11, 12, 13, 32, 33, 34, 35, 36, 37, 66, 67, 68, 69, 70, 71, 72, 43, 44, 45, 46, 47, 48, 49, 26, 27, 28, 29, 30, 31, 58, 59, 60, 61, 62, 63, 64, 65, 102, 103, 104, 105, 106, 107
OFFSET
1,1
COMMENTS
Any offset (x,y) in this spiral is a permutation of the natural numbers.
EXAMPLE
For example, if the spiral is oriented such that 1 is immediately to the left of 2, as shown below, then a(1) = 6 because 6 is immediately to the left of 1.
21--22--23--24--25--26
| |
20 7---8---9---10 27
| | | |
19 6 1---2 11 28
| | | | |
18 5---4---3 12 29
| | |
17--16--15--14--13 30
|
36--35--34--33--32--31
CROSSREFS
Cf. A068225 (inverse, right), A334751 (above), A334752 (below).
Sequence in context: A198565 A374838 A190409 * A011237 A195433 A358559
KEYWORD
nonn,easy
AUTHOR
Frank Ellermann, Feb 22 2002
STATUS
approved