A191600 Number of n X n symmetric binary matrices with each 1 adjacent to no more than 1 horizontally, vertically or diagonally neighboring 1.

2, 5, 23, 159, 1646, 28059, 724310, 29626607, 1890041732, 188477431884, 29421793928187, 7179932235630885, 2740816166752070599, 1636347059803667113339, 1527949588062203773106011

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..20

Example

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

Crossrefs

Sequence in context: A242227 A032182 A165902 * A343020 A167142 A136731

Adjacent sequences: A191597 A191598 A191599 * A191601 A191602 A191603

Keyword

nonn

Author

R. H. Hardin, Jun 08 2011

Status

approved