A191343 Number of n X n symmetric binary matrices with each 1 adjacent to exactly 1 horizontally, vertically or diagonally neighboring 1

1, 2, 6, 24, 125, 1055, 11754, 187498, 4372206, 142427556, 6649078485, 443418423639, 42015106781746, 5681500677861845, 1094937801983952063, 300642401916076713227, 117675702292067958725570

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A243806 A201158 A356634 * A368761 A052862 A277211

Adjacent sequences: A191340 A191341 A191342 * A191344 A191345 A191346

Keyword

nonn

Author

R. H. Hardin May 30 2011

Status

approved