A191553 Number of n X n symmetric binary matrices with each 1 adjacent to no more than 3 diagonally or antidiagonally neighboring 1s

2, 8, 60, 855, 24282, 1352976, 146740728, 31117674297, 12907153049676, 10462960655266920, 16578587764555196630, 51351429814865700365643, 310919919699021477652128426, 3679876610343227082947024870052

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..23

Example

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

Crossrefs

Sequence in context: A096121 A143217 A192412 * A321979 A139017 A322012

Adjacent sequences: A191550 A191551 A191552 * A191554 A191555 A191556

Keyword

nonn

Author

R. H. Hardin Jun 05 2011

Status

approved