A211049 1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors

1, 4, 48, 1232, 69944, 8897744, 2543744944, 1632807480048, 2350761948259496, 7595900369159613200, 55087633557679363709984, 896577592582670794898595216

Offset

1,2

Links

Table of n, a(n) for n=1..12.

Example

Some solutions for n=4
..2..0..1..2....2..0..0..2....1..0..2..2....2..1..0..2....0..2..1..0
..0..1..2..1....0..1..2..2....0..2..0..1....1..0..2..0....2..1..0..1
..1..2..0..1....0..2..1..2....2..0..1..2....0..2..1..2....1..0..2..1
..2..1..1..2....2..2..2..0....2..1..2..0....2..0..2..1....0..1..1..0

Crossrefs

Sequence in context: A024255 A211045 A296838 * A321076 A166231 A191952

Adjacent sequences: A211046 A211047 A211048 * A211050 A211051 A211052

Keyword

nonn

Author

R. H. Hardin Mar 30 2012

Status

approved