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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
0
1, 2, 30, 2586, 1485872, 5717794568, 141539684300104, 23071475903430624024, 24446209288705921026670236
OFFSET
1,2
COMMENTS
Diagonal of A220725
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
KEYWORD
nonn
AUTHOR
R. H. Hardin Dec 18 2012
STATUS
approved