login
A211090
1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors.
1
1, 16, 993, 236025, 215258400, 752872084911, 10098360926130825, 519450490659204066717, 102470951001660755232267828, 77521214457887124644680695382314
OFFSET
1,2
LINKS
EXAMPLE
Some solutions for n=4
..0..0..0..0....0..0..1..3....0..2..2..2....2..2..2..2....0..2..2..3
..0..2..3..1....0..0..3..0....2..2..3..0....2..0..3..1....2..0..0..2
..0..3..3..1....1..3..2..1....2..3..2..3....2..3..2..1....2..0..0..1
..0..1..1..1....3..0..1..1....2..0..3..2....2..1..1..1....3..2..1..1
CROSSREFS
Sequence in context: A187802 A181199 A024301 * A160012 A070307 A159683
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 31 2012
STATUS
approved