A185586 EKG sequence (A064413) written clockwise as a square spiral and read counterclockwise.

2, 1, 6, 4, 18, 15, 5, 10, 8, 12, 9, 3, 24, 21, 7, 14, 36, 39, 13, 26, 28, 35, 25, 30, 27, 33, 11, 22, 20, 16, 38, 42, 51, 17, 34, 32, 58, 70, 65, 55, 60, 63, 49, 56, 54, 52, 50, 48, 69, 23, 46, 44, 40, 45, 57, 19, 64, 72, 93, 31, 62, 66, 87, 29, 141, 47, 94, 92, 100

Offset: 1

Author

Paul Curtz, Feb 04 2011

Keywords

• nonn
• look

Comments

A permutation of the natural numbers.

The subsequence of primes (A000040) begins: 2, 5, 3, 7, 13, 11, 17, 23, 19, 31, 29, 47, 43, 41, 37, 53, ...

Examples

			1,2,4,6,3,9,12,8,10,5,15,18,... are written clockwise as a square spiral, then read counterclockwise: 2,1,6,4,18,15,5,10,8,12,9,3,...
The square spiral begins:
.
  33--27--30--25--35--28
   |                   |
  11  12---8--10---5  26
   |   |           |   |
  22   9   1---2  15  13
   |   |       |   |   |
  20   3---6---4  18  39
   |               |   |
  16--24--21---7--14  36
                       |
  38--42--51--17--34--32
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..10000
• J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG sequence, arXiv:math/0204011 [math.NT], 2002.
• J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG Sequence, Exper. Math. 11 (2002), 437-446.
• I. Peterson, The EKG Sequence
• Eric Weisstein's World of Mathematics, EKG Sequence
• Index entries for sequences related to EKG sequence
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

Cf. A064413.