A191602 Number of n X n symmetric binary matrices with each 1 adjacent to no more than 3 horizontally, vertically or diagonally neighboring 1s

2, 8, 52, 686, 16484, 740480, 62224406, 9743390402, 2847964953844, 1553270286186274, 1580697070071238528, 3001650015211411938494, 10635826342196669611219640, 70320933672952732438772180006

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..16

Example

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

Crossrefs

Sequence in context: A057629 A191507 A378400 * A145157 A323871 A183945

Adjacent sequences: A191599 A191600 A191601 * A191603 A191604 A191605

Keyword

nonn

Author

R. H. Hardin Jun 08 2011

Status

approved