OFFSET
1,2
COMMENTS
The path is allowed to touch but not cross itself on single points, but not on segments of any length. "Increasing" means that the (Euclidean) length of each line segment must be strictly longer than the last.
LINKS
Giovanni Resta, Illustration of a(2)-a(9)
Gordon Hamilton, $1,000,000 Unsolved Problem for Grade 8 (2011)
FORMULA
a(n) <= A160663(n-1).
EXAMPLE
A solution for the case a(8)=20 is
-------------------------
01 02 . . . . . 16
.. . 03 . . . . 14
09 . 15 . 05 . . 12
.. . 04 . . . . .
.. . 06 13 . 07 . 21
.. . 08 . 11 . . 19
10 . . . . . . 17
20 18 . . . . . .
-------------------------
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Charles R Greathouse IV and Giovanni Resta, Jun 13 2013
STATUS
approved