login
A191601
Number of n X n symmetric binary matrices with each 1 adjacent to no more than 2 horizontally, vertically or diagonally neighboring 1s
1
2, 7, 41, 428, 7588, 235992, 12750773, 1196790145, 195443817921, 55484180929526, 27388366928551712, 23507551792998353446, 35081808543792928475951, 91032423727427789694636918, 410722028606679785606473590135
OFFSET
1,1
LINKS
EXAMPLE
Some solutions for n=4
..0..1..1..0....1..0..1..1....1..0..0..0....0..0..0..1....1..0..0..1
..1..1..0..0....0..0..0..0....0..0..0..1....0..0..0..1....0..0..0..0
..1..0..0..0....1..0..1..0....0..0..0..1....0..0..1..0....0..0..0..1
..0..0..0..1....1..0..0..0....0..1..1..1....1..1..0..0....1..0..1..1
CROSSREFS
Sequence in context: A340645 A122942 A159315 * A265772 A109172 A131682
KEYWORD
nonn
AUTHOR
R. H. Hardin Jun 08 2011
STATUS
approved