A348022 The numbers visited on a square spiral when stepping to the smallest unvisited number that is visible from and shares a divisor > 1 with the current number. Start with 1 and 2.
1, 2, 4, 6, 3, 12, 9, 15, 5, 10, 14, 7, 21, 27, 18, 16, 8, 22, 11, 33, 30, 20, 24, 32, 26, 13, 39, 36, 28, 35, 25, 40, 44, 38, 19, 76, 34, 17, 68, 42, 45, 51, 48, 57, 66, 55, 60, 46, 23, 92, 58, 50, 62, 31, 155, 70, 49, 56, 63, 72, 64, 52, 65, 78, 54, 69, 84, 75, 85, 80, 94, 47, 188
Offset: 1
Keywords
Examples
The square spiral is numbered as follows: . 17--16--15--14--13 . | | . 18 5---4---3 12 29 | | | | | 19 6 1---2 11 28 | | | | 20 7---8---9--10 27 | | 21--22--23--24--25--26 . a(3) = 4 as gcd(4,2) = 2 and 4 is unvisited and visible from 2. a(4) = 6 as gcd(4,6) = 2 and 6 is unvisited and visible from 4. a(5) = 3 as gcd(3,6) = 3 and 3 is unvisited and visible from 6. a(6) = 12 as gcd(12,3) = 3 and 12 is unvisited and visible from 3. Note although 9 is unvisited and gcd(9,3) = 3 it is not visible from 3 due to 2.
Links
- Scott R. Shannon, Image of the path for the first 10000 terms. The colors are graduated across the spectrum to show the relative step order.
Comments