A213599 Number of n X n binary matrices with zero diagonal and no 2-loops or directed 3-loops (3-loop: x(i,j)*x(j,k)*x(k,i)=1, and i,j,k all different)

1, 3, 25, 549, 30535, 4168935, 1362083785, 1042729407045

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A306783 A003024 A224679 * A179473 A248417 A355123

Adjacent sequences: A213596 A213597 A213598 * A213600 A213601 A213602

Keyword

nonn

Author

R. H. Hardin Jun 14 2012

Status

approved