OFFSET
1,2
COMMENTS
Neighbors of a cell are only considered in the X and Y directions.
Number of ways to dig an n X n hole where each cell is at a different depth and water will collect in just one puddle.
Computed using a C program, brute force enumeration except using a cache of old results to cut off the search tree. For many related problems however, R. H. Hardin has coded them in S/R (which is COSPAN's language).
EXAMPLE
For n=2, 12 has only one local max., whereas 13 has two and is excluded.
........ 34 ................................ 42
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
R. H. Hardin, Oct 23 2003
STATUS
approved