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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 (list; graph; refs; listen; history; text; internal format)
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 * A030249 A000187 A053851

Adjacent sequences:  A220716 A220717 A220718 * A220720 A220721 A220722

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 18 2012

STATUS

approved

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Last modified December 14 19:27 EST 2019. Contains 329987 sequences. (Running on oeis4.)