A211051 - OEIS

A211051

1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors

1, 5, 45, 801, 27967, 1940165, 265677267, 71849269093, 38284388785363, 40154074645523977, 82859490626738386321, 336329579954192837096611, 2685093328682215861465741329

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

Some solutions for n=4

..0..1..0..0....0..1..0..1....2..0..2..0....2..2..2..2....2..1..2..2

..1..0..0..0....1..2..1..2....0..1..0..1....2..0..1..2....1..2..2..2

..0..0..2..1....0..1..2..0....2..0..1..0....2..1..2..2....2..2..2..2

..0..0..1..2....1..2..0..1....0..1..0..2....2..2..2..0....2..2..2..2

CROSSREFS

Sequence in context: A155104 A243951 A290941 * A322661 A191962 A326650

Adjacent sequences: A211048 A211049 A211050 * A211052 A211053 A211054

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 30 2012

STATUS

approved