A211079 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors

1, 10, 228, 12627, 1667397, 527301810, 398763964407, 721357961638581, 3121075294380253308, 32298409320629884228245, 799420627577762936976169203

Offset

1,2

Links

Table of n, a(n) for n=1..11.

Example

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

Crossrefs

Sequence in context: A361149 A052789 A092254 * A211084 A302095 A276019

Adjacent sequences: A211076 A211077 A211078 * A211080 A211081 A211082

Keyword

nonn

Author

R. H. Hardin Mar 31 2012

Status

approved