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A220646 Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two king-move neighbors, without 3-loops 0
1, 4, 333, 192413, 1233993907, 85240331175084 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Diagonal of A220652

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

Some solutions for n=3 0=self 1=nw 2=n 3=ne 4=w 6=e 7=sw 8=s 9=se (reciprocal directions total 10)

.00.69.47...68.49.00...68.46.48...89.68.48...68.46.48...00.78.00...00.89.00

.89.37.18...26.48.18...26.47.27...29.12.27...29.89.28...38.26.48...68.24.17

.23.16.24...00.26.24...36.34.00...00.13.00...00.12.12...26.46.24...26.34.00

CROSSREFS

Sequence in context: A135442 A086895 A293241 * A173367 A214161 A265868

Adjacent sequences:  A220643 A220644 A220645 * A220647 A220648 A220649

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 17 2012

STATUS

approved

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Last modified July 29 13:28 EDT 2021. Contains 346346 sequences. (Running on oeis4.)