A211080 1/4 the number of n X n 0..3 symmetric matrices with every element equal to one or two horizontal and vertical neighbors

0, 1, 6, 276, 19788, 4909014, 2929172742, 5071671459180, 23339078849741382, 298199841357475363224

Offset

1,3

Links

Table of n, a(n) for n=1..10.

Example

Some solutions for n=4
..3..3..2..2....3..3..3..3....1..1..0..0....3..3..2..2....0..0..2..2
..3..3..1..2....3..1..1..1....1..1..3..1....3..3..0..1....0..0..1..1
..2..1..1..0....3..1..0..0....0..3..3..1....2..0..0..1....2..1..0..0
..2..2..0..0....3..1..0..0....0..1..1..1....2..1..1..1....2..1..0..0

Crossrefs

Sequence in context: A250390 A284071 A254628 * A288796 A199097 A342983

Adjacent sequences: A211077 A211078 A211079 * A211081 A211082 A211083

Keyword

nonn

Author

R. H. Hardin Mar 31 2012

Status

approved