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A191713
Number of n X n symmetric binary matrices with each 1 adjacent to no more than 2 E, S or NW neighboring 1s
1
2, 8, 56, 760, 19792, 978304, 92183968, 16556792256, 5666183103872, 3695209097658560, 4592223914052994688, 10875252973619159084864, 49078195656242127591078144, 422056710044472651098920886272
OFFSET
1,1
LINKS
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
KEYWORD
nonn
AUTHOR
R. H. Hardin Jun 12 2011
STATUS
approved