A193811 Number of n X n symmetric 0..6 arrays with no element equal to the difference mod 7 of any two of its horizontal and vertical neighbors.

7, 186, 8064, 722340, 150684732, 82103110920, 123085880400552, 516200827188869448

Offset

1,1

Links

Table of n, a(n) for n=1..8.

Example

Some solutions for 4 X 4
..1..0..0..4....2..0..4..6....3..3..4..5....3..3..1..3....4..0..2..4
..0..2..1..0....0..6..0..0....3..2..4..4....3..1..1..3....0..1..3..0
..0..1..4..0....4..0..3..2....4..4..4..3....1..1..3..1....2..3..2..6
..4..0..0..5....6..0..2..3....5..4..3..5....3..3..1..1....4..0..6..5

Crossrefs

Sequence in context: A012843 A012798 A297765 * A296234 A219567 A202791

Adjacent sequences: A193808 A193809 A193810 * A193812 A193813 A193814

Keyword

nonn

Author

R. H. Hardin, Aug 05 2011

Status

approved