A068226 Neighbor in 2-1 direction of numbers arranged as clockwise spiral.

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

Author

Frank Ellermann, Feb 22 2002

Keywords

• nonn
• easy

Comments

Any offset (x,y) in this spiral is a permutation of the natural numbers.

Examples

			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
		

Links

• Peter Kagey, Table of n, a(n) for n = 1..10000
• Frank Ellermann, Some EIS sequences based on a spiral of natural numbers.
• Index entries for sequences that are permutations of the natural numbers.

Crossrefs

Cf. A068225 (inverse, right), A334751 (above), A334752 (below).