OFFSET
1,3
COMMENTS
This is the earliest permutation of the nonnegative integers with this property.
EXAMPLE
The spiral begins:
.
17--25--27--19--22--20
| |
21 5---8--11---7 24
| | | .
23 6 0---1 9 .
| | | | .
18 3---4---2 10
| |
16--13--15--14--12
.
The digits of the four integers inside each of the four 2 X 2 squares that contain the initial 0 add up to a prime: 0 + 1 + 2 + 4 = 7, 0 + 4 + 3 + 6 = 13, 0 + 6 + 5 + 8 = 19, 0 + 8 + (1+1) + 1 = 11. This is true for any 2 X 2 square on the (infinite) grid; the upper right corner adds up to 19, for instance: (2+2) + (2+0) + (2+4) + 7 = 19; etc.
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini and Carole Dubois, May 24 2022
STATUS
approved