A211077 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors

1, 9, 297, 30213, 9904329, 10357083063, 34636341072699, 370225462363917579, 12650055630492583306593, 1381655999590131944779825905, 482381759955085135355798493794163

Offset

1,2

Links

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

Example

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

Crossrefs

Sequence in context: A371252 A012838 A216966 * A211082 A061685 A183549

Adjacent sequences: A211074 A211075 A211076 * A211078 A211079 A211080

Keyword

nonn

Author

R. H. Hardin Mar 31 2012

Status

approved