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A220675 Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two horizontal, vertical and antidiagonal neighbors, without consecutive collinear links 0
1, 4, 43, 2024, 468036, 455249977, 2045717834201, 40852471994323068, 3654942390444289784060 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Diagonal of A220681

LINKS

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

EXAMPLE

Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)

.00.67.47...00.00.00...00.67.48...68.47.00...00.78.78...00.68.48...00.67.48

.38.36.47...00.78.00...38.00.27...23.00.00...38.23.27...68.24.27...36.48.27

.26.34.00...36.24.00...26.34.00...00.00.00...26.34.00...26.34.00...00.23.00

CROSSREFS

Sequence in context: A153255 A015084 A176827 * A222979 A284192 A278798

Adjacent sequences:  A220672 A220673 A220674 * A220676 A220677 A220678

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 17 2012

STATUS

approved

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Last modified December 3 12:45 EST 2021. Contains 349463 sequences. (Running on oeis4.)