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A191344
Number of n X n symmetric binary matrices with each 1 adjacent to exactly 2 horizontally, vertically or diagonally neighboring 1s
0
1, 1, 3, 11, 47, 294, 2274, 23217, 346865, 7054923, 194307949, 7369451741, 380583130482, 26850075718493, 2600396553939968, 344812336151621752, 62585126371789861439, 15557855832828751119291
OFFSET
1,3
EXAMPLE
Some solutions for n=4
..0..1..1..0....0..0..0..0....0..0..0..0....1..1..0..0....1..1..1..0
..1..1..0..1....0..0..1..1....0..1..1..0....1..0..1..0....1..0..0..1
..1..0..0..1....0..1..0..1....0..1..0..1....0..1..0..1....1..0..0..1
..0..1..1..1....0..1..1..0....0..0..1..1....0..0..1..1....0..1..1..1
CROSSREFS
Sequence in context: A111139 A167564 A295833 * A374983 A308538 A181278
KEYWORD
nonn
AUTHOR
R. H. Hardin May 30 2011
STATUS
approved