A211047 1/3 the number of n X n 0..2 symmetric matrices with every element equal to one or two horizontal and vertical neighbors

0, 1, 4, 102, 3452, 306196, 56305300, 23135879808, 20936361314520, 41767961477927304, 184066448459881652770, 1789009177710334924490408

Offset

1,3

Links

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

Example

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

Crossrefs

Sequence in context: A129702 A220776 A180818 * A326087 A091330 A353312

Adjacent sequences: A211044 A211045 A211046 * A211048 A211049 A211050

Keyword

nonn

Author

R. H. Hardin Mar 30 2012

Status

approved