A191713 Number of n X n symmetric binary matrices with each 1 adjacent to no more than 2 E, S or NW neighboring 1s

2, 8, 56, 760, 19792, 978304, 92183968, 16556792256, 5666183103872, 3695209097658560, 4592223914052994688, 10875252973619159084864, 49078195656242127591078144, 422056710044472651098920886272

Offset

1,1

Links

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

Example

Some solutions for n=5
..1..0..0..0..1....0..0..0..0..1....0..1..0..0..0....0..1..1..0..0
..0..1..0..1..1....0..1..0..0..0....1..0..1..0..1....1..0..1..0..1
..0..0..0..1..0....0..0..0..0..1....0..1..1..0..0....1..1..1..1..1
..0..1..1..1..0....0..0..0..0..0....0..0..0..0..0....0..0..1..0..0
..1..1..0..0..1....1..0..1..0..1....0..1..0..0..1....0..1..1..0..0

Crossrefs

Sequence in context: A135079 A084872 A254231 * A191508 A113725 A345677

Adjacent sequences: A191710 A191711 A191712 * A191714 A191715 A191716

Keyword

nonn

Author

R. H. Hardin Jun 12 2011

Status

approved