A211094 1/4 the number of n X n 0..3 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors

0, 1, 13, 679, 87781, 35830153, 43041488701, 155818927585201, 1688540173184520937, 54881098051544185333873, 5347007129460018897210926833

Offset

1,3

Links

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

Example

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

Crossrefs

Sequence in context: A157027 A042307 A012746 * A290166 A113093 A195576

Adjacent sequences: A211091 A211092 A211093 * A211095 A211096 A211097

Keyword

nonn

Author

R. H. Hardin Mar 31 2012

Status

approved