A213545 Number of n X n binary matrices with zero diagonal and directed 3-loops in at most one direction (3-loop: x(i,j)*x(j,k)*x(k,i)=1, and i,j,k all different)

1, 4, 63, 3861, 912060, 823931109, 2827364948343, 36639801307739070, 1783839514317792934491

Offset

1,2

Links

Table of n, a(n) for n=1..9.

Example

Some solutions for n=4
..0..0..1..1....0..0..0..1....0..1..0..1....0..1..1..1....0..0..1..0
..1..0..1..0....1..0..0..0....1..0..1..1....1..0..0..1....0..0..0..0
..0..1..0..0....0..1..0..0....1..0..0..1....1..1..0..0....0..1..0..1
..1..0..0..0....1..1..1..0....0..1..0..0....1..0..1..0....0..1..0..0

Crossrefs

Sequence in context: A351779 A203512 A354653 * A362386 A361683 A111444

Adjacent sequences: A213542 A213543 A213544 * A213546 A213547 A213548

Keyword

nonn

Author

R. H. Hardin Jun 14 2012

Status

approved