A220719 Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors

1, 2, 30, 2586, 1485872, 5717794568, 141539684300104, 23071475903430624024, 24446209288705921026670236

Offset

1,2

Comments

Diagonal of A220725

Links

Table of n, a(n) for n=1..9.

Example

Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)
.00.67.47...00.00.00...00.79.00...00.69.47...69.46.47...00.79.00...00.67.47
.39.39.00...69.49.00...36.47.17...00.37.17...00.13.00...39.67.14...36.34.00
.00.16.14...00.16.14...36.34.00...36.34.00...00.00.00...36.14.00...00.00.00

Crossrefs

Sequence in context: A099800 A099929 A136636 * A359665 A030249 A000187

Adjacent sequences: A220716 A220717 A220718 * A220720 A220721 A220722

Keyword

nonn

Author

R. H. Hardin Dec 18 2012

Status

approved