OFFSET
1,4
COMMENTS
a(7) > 2630.
LINKS
IBM Research, Maximal sum 6x6 grid, Ponder This December 2012.
Hugo Pfoertner, List of solutions for n=5 and n=6.
EXAMPLE
a(1) = 1: the 8 rotated and reflected matrices are equivalent
1 1 1 1 1 2 1 3 2 3 3 2 2 1 3 1
2 3 3 2 1 3 1 2 1 1 1 1 3 1 2 1
.
a(3) = 1: due to mirror symmetry, there are only 4 equivalent matrices
2 4 1 1 4 2 1 2 1 2 1 2
1 3 2 2 3 1 4 3 4 4 3 4
2 4 1 1 4 2 2 1 2 1 2 1
.
a(4) = 10:
2 1 2 3 2 1 2 3 2 1 2 3 2 1 2 3 2 1 2 3
3 4 2 1 3 4 5 1 3 4 5 1 3 5 2 1 3 5 4 1
1 5 3 4 1 2 3 4 1 2 3 4 1 4 3 4 1 2 3 4
3 2 1 2 2 3 1 2 3 2 1 2 3 2 1 2 2 3 1 2
.
2 1 2 3 2 1 2 3 2 1 2 3 3 1 2 3 3 1 2 3
3 5 4 1 4 3 4 1 4 3 5 1 2 3 3 1 2 3 3 1
1 2 3 4 1 2 5 3 1 2 4 3 1 4 5 2 1 5 4 2
3 2 1 2 2 3 1 2 2 3 1 2 3 2 1 3 3 2 1 3
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Hugo Pfoertner, Sep 22 2020
STATUS
approved