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A220687 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly two horizontal, vertical or antidiagonal neighbors 1
1, 1081, 362057, 128995678, 42362190063, 14108684022136, 4701615485821782, 1566852499542855296, 522108399243273023731, 173978947909208417520148, 57974051497341052095013087, 19318375776055542860988503113 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 7 of A220688

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..114

EXAMPLE

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

.00.00.67.46.46.47.00...00.00.00.00.68.48.00...00.00.68.48.68.46.48

.00.36.46.47.37.67.47...00.67.48.00.27.26.47...00.78.28.28.26.47.28

.00.00.36.34.36.34.00...36.46.24.36.46.34.00...36.24.26.24.36.46.24

CROSSREFS

Sequence in context: A251199 A220334 A221295 * A188240 A165809 A332069

Adjacent sequences:  A220684 A220685 A220686 * A220688 A220689 A220690

KEYWORD

nonn

AUTHOR

R. H. Hardin Dec 17 2012

STATUS

approved

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Last modified September 25 18:27 EDT 2022. Contains 356986 sequences. (Running on oeis4.)